July through Sept
A. SPEAR 3 PROJECT SUMMARY
1. Technical Progress
The gradient dipole (145D) prototype was completed. Magnetic measurements at IHEP and at SLAC confirmed the required field quality and full production is underway. The first quadrupole (34Q) was also completed with excellent results for both electrical and mechanical tests. Details of optimization of the pole tip and chamfer are provided in Section 1.1. Sextupole laminations are being analyzed for final approval. The engineering design for the combined function horizontal/vertical correctors has been completed; fabrication plans are underway. Also, the design of the magnet support system on the arc girders is complete.
The QFC, BM1, and BM2 vacuum chambers have been designed for the magnet systems on the arc girders. The first machined QFC units from our production contract were received in June and e-beam welded this quarter. Machined parts for the longer BM1 and BM2 chambers have also been received and await e-beam welding. The design of Invar supports to the main girders is also completed. In addition the detailed design of the orbit kicker magnet for injection is complete and the designs of in-vacuum diagnostics (synchrotron light monitor, beam scrapers, and beam stopper) were initiated.
Designs and specifications for many of the magnet power supply systems are complete and purchase orders are scheduled over the next six months. General plans for installation in the existing power supply building are in preparation.
Fabrication of the four PEP-II style RF cavities is continuing on schedule together with cavity accessories including high order mode loads, tuners, and coupling networks. The waveguide layout design for the new Klystron location in the West straight section is complete.
A design review was held September 20 in which the plan for computer control hardware and software development was presented and endorsed. Design work is proceeding on the fast digital power supply controller, BPM timing/crate driver, synchrotron light monitor system, signal generator for master oscillator, as well as orbit and vacuum interlock systems.
Most of the annual scheduled down-time for SPEAR maintenance occurred during this quarter. In both the East and West straight sections, SPEAR 3 work included the construction of new concrete foundations in the pit areas (required for SPEAR 3 magnet supports), new shielding walls (roof blocks will come next year), and new entry mazes. The work was completed on schedule while costs were ~70% above baseline. There was only one bidder for the contract in a busy construction area.
The above new shielding walls incorporated all of the cable tray penetrations for the SPEAR 3 cable plant as well as wall supports for future trays. Work has continued on plans and design of outside cable tray supports.
The accelerator physics effort has focussed on software development, specifications for beam diagnostics, beam stability studies, and the analyses of the adequacy of measured prototype dipole and quadrupole fields. The orbit control applications program has been upgraded, the optimum location of synchrotron light monitors has been investigated, and the design of beam scrapers has been studied in concert with the vacuum group.
2. New Project Baseline
Near the end of the last report period (June 13-14, 2000) a DOE Lehman review committee conducted the third Technical and Management review of the SPEAR 3 project. The review report noted that "The management structure and dedicated staff are in place to effectively execute the project and …. the project team has made very good progress on the development of designs for the technical components and conventional facilities."
At this review the SPEAR 3 Team pointed out that the funding profile presented to the project at the first DOE quarterly review (3/28/00) would delay the project up to two years. A revised funding plan was provided to the project on June 21, 2000. The impact of the plan was reviewed in terms of schedule impact, manpower requirements, and associated obligations and costs for the project.
The revised project plans associated with the revised funding plan were presented at the August 7, 2000 DOE quarterly review. The overall impact is a one-year delay of project completion to the end of FY 03 with a 5M$ increase in project costs. This is now the official project plan.
During this quarter, the detailed schedule with associated milestones have been revised to match the revised plan and the PMCS system has been updated such that earned-value tracking could begin for this quarter of FY 00.
The revised SPEAR 3 cost estimate at WBS level 2 is provided in Table
1 where the new total cost of 58M$ is indicated. The new DOE/NIH funding
profile is presented in Table 2 together with the revised obligation and
cost profiles. The associated revised milestones for the project are given
in Table 3. The status of total project costs through September is summarized
Table 4 provides the BCWS, BCWP, and ACWP with associated variances
at WBS level 2 for the project beginning with this reporting period for
the new baseline. In line with the above changes, the Project Execution
plan has bee revised and presented to DOE for approval.
|1||SPEAR 3 Project|
|1.3||Power Supply System||
|1.5||Instrumentation, Control & Protection Systems||
|1.7||Beamline Front Ends||
|1.9||Installation & Alignment||
|1.A||Project Physics, Management & Administration||
Total Direct in FY 99 M$
Total Direct + Indirect in FY 99 M$
Costs plus Escalation
TOTAL ESTIMATED COSTS (TEC)
SPEAR 3 Revised Plan
|Revised Project Milestones|
|The Project key milestones are as follows:|
|MILESTONES LEVEL 1 - Office of Basic Energy Sciences Approval|
|Approval of CD1 (Mission Need)||
|Approval of CD2 (Baseline Approval)||
|Approval of CD3 (Project Start)||June 1999|
|Approval of CD4 (Start of Operations)||February 2004|
|MILESTONE LEVEL 2 - DOE SPEAR 3 Project Office Approval|
|RF Cavities Ordered||November 1999|
|RF Klystrons Ordered||December 1999|
|Main Magnet Designs Complete||January 2000|
|Arc Vacuum System Design Complete||February 2000|
|Safety Review - PSAD approved||December 2000|
|Start Vacuum System Production||April 2000|
|Test Magnet Prototypes||October 2000|
|Start Magnet Production||October 2000|
|First Magnet Raft Assembled||December 2001|
|Complete RF System Production||July 2002|
|Complete Magnet Production||December 2002|
|Final Safety Analysis Document Approved||January 2003|
|Complete Vacuum System Production||February 2003|
|Complete Raft Assembly||April 2003|
|Start Major Installation||May 2003|
|Start Commissioning||November 2003|
|Accelerator Readiness Review Completed||December 2003|
B. Detailed Reports
Supports System1.1 Magnets and Supports
Figure 1.1. SPEAR3 Standard Cell Girder
The support system designs have been investigating alternatives to the rigid girder design that has been presented at the last Lehman review (see figure 1.1). This is being done to ensure that SSRL has considered the option and not limited the future capabilities of the storage ring. The alternative being investigated is the cam supported, 6 degrees of freedom (DOF), design which is used at the Swiss Light Source (SLS). The SLS design used the approach that was developed at SLAC for the FFTB magnets.
The greatest difference between the successful FFTB and SLS cam support system and SPEAR3 is the component weight and allowable height from floor to beam center (see figure 1.2). The FFTB system mostly supported individual magnets while the SLS design supports a girder that has a complement of magnets attached to the girder. The weight of the SLS complete girder with magnets is approximately 9 tons with a distance of 53 inches from floor to beam center. SPEAR3, on the other hand, has a girder weight close to 13 tons and a distance of only 42 inches from floor to beam center. This SPEAR3 weight plays a large factor in the design of the system, mostly in attempting to meet the stringent earthquake standards in California. The SLS design does not have hold-down restraints and earthquake criteria is not implemented at their laboratory.
Another constraint in SPEAR is the limited distance between the storage ring and the existing beamline support structures. This area is designated for the LCW pipe distribution system and the magnet bus cabling and at present we have an interference between a cam design and this area.
While the preliminary cam system design is being studied we are continuing
to complete the rigid girder and strut design details. We have received
the rod-ends for the prototype magnets and have fabricated the hardware
for mounting these magnets. After mounting the hardware on struts vibration
measurements will be done to determine the resonant frequency of each component
and compare this to the engineering model.
Fig. 1.2 Cam Support Preliminary Design – SPEAR3 and SLS
SLAC received the Gradient Dipole prototype (145D) from IHEP in early July and proceeded to complete the magnetic measurements. The results of the magnetic measurements and other verification tests were positive and full production approval for the 145D magnets was given to IHEP in early September. Approval was also given to IHEP to produce the first 109D dipole with full production pending magnetic measurement results from IHEP to verify that the end pole chamfer developed for the 145D is correct for the 109D.
IHEP completed the 34Q Quadrupole magnet prototype in mid August (see picture below) with excellent results in both mechanical and electrical tests. IHEP and SLAC magnet engineers completed 2 iterations of the end pole chamfer design and magnetic measurements before reaching the final design that was cut into the prototype. The 34Q magnet is ready to ship to SLAC after inspection by SLAC project members during a scheduled early October visit to IHEP. See Magnetic Measurements section below for details of dipole and quadrupole measurements.
34Q Quadrupole prototype completed at IHEP
IHEP has completed the tool and die punch for the sextupole magnets, punched several laminations, and sent them to SLAC and to a commercial location in Beijing for CMM measurements. The laminations arrived at SLAC in late August and have undergone the coordinate measurements with small deviations found at the pole tip and other non-critical areas. SLAC will do an analysis of the changes to verify the magnetic properties of the magnet before giving approval to IHEP for production stamping and is schedule to be done in early October. See Magnetic Measurements section below for details of CMM data.
The preliminary engineering design for the combined horizontal and vertical
corrector has been completed (see fig. 1.3). The design includes optimization
of the conductor placement for the current dominated vertical corrector
and evaluation of issues associated with field penetration due to coil
and chamber eddy currents. A set of mechanical drawings for the construction
of the magnet was made and delivered to IHEP for evaluation and cost estimate.
Figure 1.3 - SPEAR3 Horizontal/Vertical Corrector Magnet
Gradient Magnet. The prototype 1.45 meter long SPEAR3 gradient
magnet was constructed with removal pole end inserts (Figure 1.4). The
depth of the chamfer cut in the inserts was determined by measuring the
nonlinear distribution of the field integral. The optimization of the chamfer
shape was performed at IHEP in China during April and May, 2000. Approval
of the final chamfer shape was made during a visit to IHEP in June, 2000
by Richard Boyce, Nanyang Li, Domenico Dell’Orco and Jack Tanabe.
Figure 1.4 – Gradient Magnet Pole Tips
The prototype gradient magnet was shipped to SLAC where the measurements
were repeated using a duplicate compensated coil. The cross sectional dimensions
of the coil, which is 2 meters long, is shown in the Figure1.5. Small differences
among some of the coil dimensions cause small differences in the measurement
Figure 1.5 Details of measurement coil
Figure 1.6 Comparison of SLAC/IHEP measurements
Measurements made at IHEP were reproduced at SLAC (see Figure 1.6).
The prototype performance met the specified requirements at 3.0 GeV. It
appears that the field quality falls off a bit at the edge of the required
good field region at the required current for 3.3 GeV operation.
Quadrupole. The quadrupole pole design is scaled from the ALS and PEPII designs. The pole end chamfer was initially developed empirically using the ALS quadrupole prototype. The SPEAR3 initial chamfer design was an extrapolation on the ALS design based on the ALS performance and studies using the three dimensional magnet code, AMPERES. Measurements of the prototype magnet indicated that the "allowed" multipole spectrum (n=6, 10, 14, 18, …) marginally met specifications for operation at 3.0 GeV . (Preliminary studies of the dynamic aperture specified when evaluated at the good field aperture radius, 32 mm.) The n=6 multipole error is the most important error since the higher order terms, n=10, 14, 18, … diminish as the 8th, 12th and 18th power of the radius, respectively whereas the n=6 multipole error diminishes as the 4th power of the radius.
Preliminary rotating coil measurements of the prototype were made at
IHEP during September, 2000 and sent to SLAC for analysis. These measurements
indicated the presence of a large sextupole field. This field is due to
the earth’s magnetic field, which in the absence of flux carrying (steel)
legs, creates a small static spectrum of odd multipoles. The sextupole
component appears to be the most serious. The size of these fields was
verified in a series of POISSON magnet calculations. The flux distribution
from these calculations are illustrated below (see figure 1.7). At this
point, a study was initiated to determine whether the stainless steel legs
should be replaced with iron (flux carrying) legs.
Figure 1.7 POISSON run showing flux distribution from earth magnetic field
The legs of most of the magnets need to be asymmetric to provide clearance for the vacuum antechamber and photon lines. Although iron legs will shield the electron beamline from the environmental field, POISSON studies indicated that asymmetric iron legs will introduce larger errors than those introduced by the environmental fields; therefore, it was decided to keep the original stainless steel legs.
The first measurements of the allowed multipoles are shown below (Figure
1.8) for various currents.
Since operation at 3.3 GeV is a future upgrade option, it was decided to attempt to reduce the normalized n=6 error multipole by making a small change in the chamfer. A curve from Klaus Halbach’s perturbation paper was used in order to develop a chamfer which would change the n=6 multipole without changing the n=10 or 14 error multipoles. The curve and theory predict that removing a small section of the pole tip from 0 to 13 degrees on either side of the pole center would alter the n=6 multipole without changing the other multipoles.
The suggested chamfer modification is a small cut at the end of the
present pole chamfer as shown below (Fig. 1.9). The details of the cut
are analyzed in Fig. 1.10
With this new chamfer, the n=6 normalized multipole was reduced from
for 3.0 GeV operating current and
for 3.3 GeV operating current as shown in Fig. 1.11
Sextupole. Sextupole approval laminations were sent to SLAC where
they were measured on the CMM by Mike Starkey. The overall shape is illustrated
below (Fig. 1.12)
A scaled up view of the critical pole area is illustrated below (Fig.
1.13). The illustration compares the horizontal pole, the vertical pole
mirrored about the 60 degree line and the ideal pole defined by the design
drawing. The largest discrepancies occurred near the pole edges where a
0.625 inch radius is prescribed.
Since the CMM measurements are subject to errors at points near curved shapes, a scan was made of the pole end. The following illustration (Fig. 1.14) is an 8X high resolution scans of the pole profiles shown with a precision machinist scale. The machinist scale major divisions are 0.100 inch and the minor divisions are 0.020 inch. The tolerances on the profile are +-13 mm (+-0.0005 inch). The scans were made primarily to compare with radius profile with the required profile. The circles drawn at the corners of the poles are 0.125 inch diameter circles.
Based on the measurements and the scans, approval was given to IHEP to proceed with the stamping of the prototype magnet laminations.
Figure 1.14 Image of Sextupole lamination pole tip profile
1.2 Vacuum System
During this quarter, the efforts of the vacuum group have been the following;
SSRL received two BM-2, one BM-1 and one QFC standard girder chamber halves (top and bottom) this quarter. After receiving the first set of QFC plates in June, a thorough manufacturing development program was started. The plates were repeatedly measured to quantify the effect of each welding step. This was necessary to understand the potential movement of the chamber during welding and to determine the final manufacturing tolerances that are achievable. The profile and alignment tolerances of the slot are crucial to prevent the high intensity insertion device light from striking the chamber. Also, the chamber tolerances are important to prevent magnet and vacuum chamber interferences. The clearances between the magnet and vacuum chamber are as small as 2mm.
Figure 2.1 BM-1 & BM-2 machined chamber halves
The majority of welding was completed on the first article QFC chamber during this quarter. During the next quarter we will complete the welding of the eddy current break, BPM, end flanges and absorber. The welding of the chamber was straightforward and no difficulties were encountered except for the welding of the eddy current break. Modifications are being made to the eddy current break to decrease the heat required for weld. Results from the first article QFC chamber show that the required tolerances are achievable with the current design. The fabrication process on the BM-2 plates has also started. A brief summary of the first QFC fabrication process is written below,
1. QFC halves received and dimensionally inspected in the restrained and unrestrained position. Large deflections were observed in the horizontal plane. Features met the drawing tolerances.
2. Parts assembled in welding fixture. Profile and slot were inspected and found to be within tolerance band.
3. Plates disassembled and mechanically straightened and re-inspected dimensionally.
4. Parts reassembled in weld tooling. Slot height re-measured and found to be within tolerance band with no appreciable change.
5. Parts disassembled and cleaned.
6. Cooling bars were welded to the machine halves. As anticipated the halves bowed from the welding. The parts are reassembled and the slot height re-measured. Dimensions are within tolerance band with no appreciable change.
7. Halves are disassembled and re-straightened after welding.
8. Parts reassembled and re-measured before welding.
9. Main box weld is performed and the slot is re-measured. Dimensions within tolerance band.
10. Eddy current break was welded. Difficulties with the weld joint were encountered and modifications are required. Weld was not completed.
11. Side cooling bars were welded to the chamber.
Figure 2.2 Welded QFC Chamber
Although the assembly of the first article QFC chamber went well, we have not given approval to continue the production machining of the chamber halves. The plates received from the vendor, Stewart Tool, had larger deflections than expected. The prototype chamber halves that were machined last year by a different company, led us to conclude that the machining of the plates would produce acceptable parts. It was understood that machining of copper is difficult, but these parts required significantly less machining than copper chambers of similar size that were machined for PEP-II. However, the different vendor machined the prototype chamber halves and the material was from a different producer of copper plate (Revere), than the production QFC halves.
The excessive deflections seen from machining indicated that the problem
was mainly due to the copper material. Copper plate was located from the
same lot as the prototype halves and sent to the current vendor, Stewart
Tool, to machine another set of QFC chamber halves. Stewart found that
the deflections in the QFC plates made from the Revere material were significantly
smaller than the plates machined from the Otokompu copper that they purchased.
Both the prototype and production drawings specified C10100 H02 (half hard),
class 2 or better copper. However, the prototype material was shown to
be just below the minimum tensile strength of the half hard specification
(35.5 ksi) and the production material was at the low end of the half hard
specification (37.5 ksi). Currently, we believe that using the Revere copper
would reduce fabrication costs and difficulties, however, there would be
re-stocking fees and schedule delays. We are still evaluating the differences
in the material and determining if reducing the tensile strength requirement
for the material would be acceptable. A decision will be made shortly based
on machine performance, cost and schedule.
Figure 2.3 Assembly of BM-2 Chamber
Figure 2.4 End View of BM-2 Chamber Assembly
The first set of tooling for the QFC chamber was completed, as well as the majority of the BM-2 tooling. Work on the BM-1 chamber tooling has also progressed and will be complete by the end of the year. The first set of QFC chambers demonstrated that the tooling was a success.
In terms of staff, we added personnel to help with production coordination of the standard chamber and to complete final documentation and release of all the detail drawings and their related 3D models.
Titanium Sublimation Pump (TSP)
TSP testing continued this quarter. The test stand was calibrated by performing numerous tests with a constant pressure and fixed volumes of gas. Both N2 and CO were used to test the first pump and calibrate the stand. Also, gauges were matched and linearized. The pump tests indicate that the test stand is accurate to about 10 to 20 percent.
Tests performed using TSP prototype1 showed that the filaments only sublimed about 50% of the fin surface. Engineering estimates assumed that an 80% coverage could be achieved. Therefore 50% coverage is approximately a 40% decrease from the expected capacity of the pump. Also, the low capacity of the pump indicated that frequent sublimations would be required to maintain a pumping speed of 1000-1500 L/s. Due to the initial results, a simple modification was made to the second prototype pump to improve the sublimation coverage. The filament was reoriented from a vertical position to a horizontal position. This modification increased the sublimation coverage to 80%. Also, by reorienting the filament the pump length could be increased and therefore increase the surface area by an additional 50%. The additional pump length was not added to the second prototype TSP at this time.
The second prototype pump testing using N2 show that the capacity for N2 (H2 and O2 are also present in the system) is 0.25 Torr-Liter and for CO (and CO2) the capacity is 0.5 Torr-Liter. The vacuum system expects a gas load that consists of 80-90% H2 and 10-20% CO. TSP’s have an enormous intrinsic speed for H2 and studies have shown that a N2 equivalent is a good estimation for vacuum studies. The test results clearly indicate that the TSP is not "conductance limited." In other words, the speed of the pump will not result in a fairly constant net pumping speed until the TSP is nearly spent.
Also, engineering analysis confirm the experimental results. If the pumping speed of the pump was derated from 1500 to 1000 L/s, the average pressure in the injection straight would be increased from 1 h torr to 1.1 h torr, and the expected flashes would be every two days. Other machines have found that the engineering estimate can be over conservative by a factor of three.
Interpretation of the experimental and analytical data combined with the operational experience of TSPs employed in a similar manner is under investigation. At this time, testing on pump 2 is continuing, as well as, studying design changes to improve the overall capacity of the pump. The change in filament orientation will increase the capacity by 50% more than the second prototype pump. It is also possible to modify the fin geometry to increase the capacity.
The final design and analysis of the absorbers were completed this quarter. The drawings were also finalized and the first article fabrication is underway. The first set of absorbers will be complete by next quarter.
Standard Girder Supports
During this quarter the action items from the preliminary design review were addressed. Three-dimensional models of all the supports were completed and vacuum-to-support-to-girder interfaces were verified. Detail drawings of the BM-2 supports are near completion and all of the remaining support detail drawings should be complete by next quarter.
Figure 2.4: BM-2 Chamber mounted on the Support Girder
The time extension for the SPEAR3 project has allowed the Girder engineering group to produce a prototype. Therefore, it was decided to produce the BM-2 vacuum prototype supports and delay the production order. To make the prototype economically viable the low expansion Y supports will be made from carbon steel instead of Invar. The primary objective of the prototype girder assembly is to verify clearances, assembly procedures, and cable and water hose routing. It would have been advantageous for the vacuum group to gain experience on manufacturing the low expansion supports, but the prototype cost could not be justified. However, a qualified vendor who has extensive experience producing Invar low expansion structures was found. The prototype construction of the BM-2 supports will be complete early next year. Production orders will be placed as soon as the prototype girder assembly is built and a final design review of the girder and supports is complete.
Matching Girder Chambers
The preliminary layout of the matching girder "A" and "B" commenced this quarter. The lattice allows the chambers to be shortened by adding flange pairs. Therefore, there will be more than one chamber associated with a matching BM-1 and BM-2 girder. Also, the lattice could be modified to accommodate the same QFC chamber as the standard QFC chamber for both matching cell "A" and "B". This could significantly decrease non-recurring engineering costs and fabrication costs of "one-off" matching chambers.
The major action items from the preliminary design review were addressed. Drawings of both the K1 (.6 m) and the K2 (1.2 m) long magnet vacuum chamber were completed this quarter. The prototype fabrication of the injection kicker started and completion is expected in December. The prototype will be used to verify the magnetic performance of the kicker and its related hardware that is being developed by SLAC and SPEAR 3 Power Conversion groups. The prototype will be also used to measure higher order modes (HOMs) and to verify if HOM loads are needed. It will also be used to prove out the mechanical design and fabrication.
Test parts for the HOM testing apparatus are also in development. We are hoping to send these parts to LBL for calibration of the test stand as soon as possible.
The design of the septum chamber, the mating transition chambers, the synchrotron radiation masking and the septum bellows are near completion. The injection design staff was able to refocus their attention on the septum chamber this quarter. Work will continue next quarter on the detail design and analysis, however, a final design and review is pending on the completion of the septum magnet design.
The design of the RF straight is near completion and a final review is still expected by the end of the year. During this quarter work on the design continued and thermal and vacuum calculations were performed. Revised mis-steer values for this area are anticipated and will result in relocating the masks. Also, HOM calculations are required in this area due to the masking geometry currently required to protect the RF cavities from an SR strike. The final design and analysis is pending on the mis-steer values and HOM calculations.
The diagnostic components for the ring have started early. The overall layout of the diagnostic components is being re-evaluated in an attempt to use only one straight instead of two dedicated straight sections. Since straight section space is extremely valuable for future insertion device upgrades, it was determined that spending time on combining diagnostic components into the RF straight and kicker straights was worthwhile.
Physics, engineering, and functionality specifications for all the diagnostic components are being developed. Also, design information from other labs is being gathered and studied. Initial rough concepts along with ray traces and preliminary thermal calculations are being performed to determine the minimum space needed for these diagnostic components.
The synchrotron light monitor (SLM) optical requirements are still being established. The engineering staff is working with the responsible physicists to develop initial optics to get the light to the main optical processing area. Preliminary layouts of both a horizontal and vertical mirror with a "cold finger" mask were produced. Also, an attempt to modify the existing beam line 1 (BL1) port for the SLM was studied. It was determined that the light available for the SLM may not be adequate and that future science needs could prove that using BL1 was shortsighted. The focus returned to placing the SLM in a dedicated straight that would also house the tune monitor and tune driver chambers.
Development of mechanical and accelerator operational requirements on
the horizontal and vertical scrapers, the beam stoppers and the PPS stoppers
have also progressed. The current plan for the machine is to have the scrapers
also function as the operational beam dump. In the past, SPEAR2 has used
the PPS stoppers as the beam dump. Due to the higher current and energy
in this machine, it was decided to use the scrapers to dump the beam. The
PPS stoppers are the third line of defense and other machines have shown
that the stoppers almost never intercept beam. Therefore, they do not need
to survive numerous direct beam hits, but they need to prevent personal
injury and they require a disaster monitor to positively indicate that
the device has been compromised. Unlike the PPS stopper, the scraper intercepts
some sigma of the beam on a regular basis and must be designed to handle
large heat loads. Therefore, the scrapers could be designed to dump the
beam by clipping enough of the beam power to significantly reduce the lifetime.
Investigation into the thermal heat loads and cyclic thermal stress loading
of the scrapers is in progress.
Dipole Power System
During September Neeltran submitted the required seismic analysis for the dipole power transformer. SSRL’s review indicated that the seismic analysis was generally satisfactory. Review commentary was returned to Neeltran and they were asked to incorporate the following comments into the transformer design and seismic analysis:
Neeltran also submitted the transformer flux density, inrush current and core and winding temperature calculations. These are presently undergoing SLAC/SSRL review. Return of SLAC/SSRL comments and/or acceptance of the calculations will occur during the next reporting period.· Indicate an originator, approver, edition number, date and the SLAC/SSRL purchase order number in the seismic analysis document.
· Cite the 1997 edition of the Uniform Building Code (UBC) referenced in the analysis to conform to the latest published edition of this code.
· Change the 6 individual "L" tie-down brackets previously suggested by
SLAC / SSRL to 2 "L" tie-down channels that run the depth of the transformer on both ends. Also, Neeltran was asked to increase the number of tie-down holes required by Specification M-339 from 6 to 8.
· Provide tests or documented evidence that the transformer can be lifted by its eyebolts and that the enclosure can be lifted by its eyebolts with the transformer mounted inside. The use of swivel hoist rings in lieu of eyebolts is suggested, as these will withstand greater side loads than eye bolts. SSRL attached an excerpt from a Carr-Lane swivel hoist ring catalog for Neeltran information.
The technical/purchase specification for the 930kW Dipole Power Supply was subjected to internal interdisciplinary review. Coincident testing of a similar 12-pulse rectifier for SPEAR 2 revealed the need for freewheeling diodes across each series-connected bridge in order for the rectifiers to properly conduct load current. This need has been incorporated into the SPEAR 3 dipole power supply specification. The specification was approved for issuance of a request for proposals (RFP). The bids from industry are due on November 17th.
Other Unipolar Power Supplies
During the next reporting period the specification for the freestanding, intermediate (relative to the dipole power supply) size power supplies will be started.
Bipolar Power Supplies
The use of a totally digital interface in the bipolar power supplies was investigated in an attempt to possibly eliminate analog-to-digital and vice-versa conversions in the bipolar power supply multi-channel controllers. The investigation revealed that although theoretically feasible, the unique volt-second feedback scheme used in the power supplies did not readily lend itself to digital conversion at this time. However, the power supply layout will be designed to accommodate a later upgrade to digital if and when the technology is available and needed. At the present time the power supply design is proceeding on the basis that the interfacing, fast, multi-channel power supply controllers will have onboard A/D and D/A converters.
The design of a 4-stage, full-power prototype kicker pulser, rated 7.5kV, 2.6kA and based on K2 magnet requirements has been completed. During this reporting period all of the needed prototype electronic parts were received. All of the mechanical parts have also been received. Some in-house machining of the mechanical parts is needed and is currently underway. Fabrication and assembly of the prototype pulser will be completed by the end of the next reporting period, with testing scheduled to occur immediately thereafter.
Single Channel Power Supply Controllers
The parts that are crucial to the single channel controllers and which
might be in future short supply were purchased and have received. Specifically,
the parts are the Intel 8044 controller, the ADCs and DACs and a custom
+/- 15V power supply. These parts are being held in secure storage until
Fabrication of 4 RF cavities at Accel Instrumentation in Germany is on schedule:
Fabrication of cavity accessories at SLAC including ceramic windows and higher order mode loads is making rapid progress:· Cooling channels in 4 cavity bodies are machined (See Figure 4.1); electro-plating has started on two cavities slightly ahead of schedule.
· Process qualification samples are mostly complete including a different process of attaching the cooling channel stubs.
· Attaching mounting blocks to the electro formed copper still has to be verified but earlier tests are promising. (Delivery of the cavities is scheduled for fall 2002).
The 1.2 MW klystron was ordered March 17, 2000 with Marconi Applied Technologies with a 12 month delivery time. We suggested a different supplier for the cathode used in this tube which the vendor is trying to accommodate. This will hopefully improve the outgasing performance of the klystron.· All twelve high order mode loads are completed.
· The ceramic windows had a faulty first braze test, indicating a loss of the know-how at an external vendor. This process will get more attention.
· Other components like tuners and coupling network are 90% complete.
The waveguide layout design is complete and drawings are signed off.
The Low-level RF System design modifications have slowed down since
two of the key engineers have left SLAC. The LLRF effort is presently being
reorganized using other knowledgeable personnel in the SLAC Controls group.
Figure 4.1 Cavities
1.5 Instrumentation and Control Systems
Work by the SPEAR 3 Instrumentation and Control (I&C) group during the last quarter of the project has focused on the continuing specification of computer control, BPM processing, timing and protection system components. Detailed design of specific components has begun. An in-house engineer has been identified who might replace the digital signal processing engineer that left the group last quarter. Progress for various systems is summarized below:
1. Computer Control System
2. Beam Monitoring Systems
- An internal SLAC design review was held September 20 at which the plan for SPEAR 3 computer control hardware and software development was presented. The overall plan was endorsed and several action items were identified. The primary action is to complete written descriptions of each software module that will be used for system documentation and as part of the specification of work for any modules that will be delegated to the SLAC software group.
- Two Power PCs have been received for initial development of EPICS IOC and Orbit Feedback processing functions. The VxWorks operating system has been installed on these CPUs and software development work is commencing. One of the first tasks will be to communicate with the newly arrived digital IF Processor module (see below).
- Work is continuing on the design of the fast digital power supply controller. ADC, DAC and CPU candidates have been identified and evaluation boards have been received. Tests of the CPU software configuration have begun. Preliminary specifications of the digital regulation and filter algorithms for power supply control and monitoring have been completed and more detailed specifications are in progress.
4. Timing System
- The design concept for the BPM RF/IF Converter modules is developing. The decision of whether to pursue a 4:1 switched button design or a parallel button processing design will be made during the next quarter. In either case, it is likely that a specification will be written for outside vendor design and fabrication of the RF-IF converter system.
- The first 2 IF Digital Receiver modules from Echotek have been received and in-house testing should be complete by the end of October. One critical test will be to see if a shifted-frequency calibration signal can be processed in parallel with the beam-related signal with an amplitude resolution on the 0.001 dB level. If so, the parallel-button RF-IF processing scheme may be adopted.
- The BPM Timing/Crate Driver (T/CD) module design is 90% complete and is on-hold until a decision regarding switched-button or parallel-button RF processing is made. This decision will affect the final configuration of the T/CD module.
- Development of the orbit feedback processing algorithm is on-hold until the DSP engineer replacement is identified.
- The BESSY II mechanical design drawings for the image current-carrying shroud for the DCCT have been received are being reviewed for adaptation to SPEAR 3.
- The design for the UV and visible light synchrotron light monitor is in progress.
5. Protection Systems
- A PTS DDS-based signal generator has been ordered that will serve as the SPEAR 3 RF master oscillator. The unit has very low phase noise and phase-continuous frequency switching.
- Procurement specifications for the LO/Clock and Booster-SPEAR Phase-Locked Loop systems are being reviewed and refined. An order to Wenzel, Inc. for the systems is planned during the next quarter.
- The first phase of PPS Access Control interlock modifications for the modified SPEAR tunnel has been completed. A decision on eliminating the search areas in the East and West shielding areas will be made in the next quarter. This will determine the next phase of Access Control interlock modifications.
- A design review of the new digital Average Current Monitor system for the Beam Containment System was held in September. A prototype unit has been built and is being tested at the SSRL Gun Test Facility. The design was approved with minor modifications, but adopting the system for official use is dependent on policy decisions by the SLAC Radiation Safety department regarding computer-based safety systems. This issue will be addressed by the Radiation Safety department in the next few months.
- The design of the Orbit Interlock has begun. A pair of BPM processors and associated support hardware is being ordered for testing from Bergoz, Inc. Interlock processing CPU options are being considered.
- More detailed requirements for the Vacuum Protection system are being identified by the Vacuum group. These include thermocouple, flow switch, and vacuum pumping needs. Detailed design of the protection system will proceed in about one year.
1.6 Cable Plant
The quarter corresponded with the scheduled SPEAR2 maintenance period, which began on 07/04/00 and ended on 10/09/00. Consequently, work on the SPEAR3 Cable Plant shifted from design to the early stages of implementation.
New concrete shielding walls were poured in the East Pit, the West Pit, and at Beam Line 2. The completed walls incorporated all of the cable tray penetrations specified for the cable plan, as indicated in the drawings supplied to the contractor. The specified strut supports were also imbedded into the concrete walls. These will later be used to mount cable tray.
In the two pit areas, existing cables were relocated to accommodate the construction work. This involved disassembling cable tray and temporarily supporting cables using ropes. Some unused cables were identified and removed. Once the concrete walls were completed, sections of new tray were assembled, and the cables replaced. These SPEAR2 cable trays use wall penetrations different from the SPEAR3 penetrations, so that SPEAR2 cables are not disturbed by SPEAR3 cable installation.
The pit area work also impacted cables with destinations in these areas. Cables for four BPM stations were dressed back into place, and reconnected to the associated button pickups. Approximately 15 other coaxial cables in the East Pit were identified as unused and dressed out of the way for SPEAR2 operation.
Phase I of the Main Control Room re-design was completed during this period. This consisted of removing two dated relay racks, the addition of three new racks, and related improvements. The new rack installation is adherent to the latest code requirements and instrumentation methodologies. These included electrical safety, ampacity needs, seismic restraint, EMI shielding, dust control, and general safety. The SSRL ES&H department and the SLAC Seismic Committee approved the design. Phase II of the work is scheduled for the 2001 maintenance period, and will consist of the elimination of 10 dated racks, the addition of 8 new racks, and a 40% increase in work area floor space. Console work surface will increase by 80%. The new racks are deep enough for the largest commercially standard equipment.
A small amount of SPEAR2 electronics was decommissioned from the control room, and unused cables were pulled from the under-floor cable trays. The SLAC Salvage department processed all cable material removed during the period.
Cable Plant design work continued. The cable weight estimates were revised
downward by about 5%. The supports for new 30" cable trays in the East-West
overhead tray run are being revisited. The goal is to lower the tray elevation,
thereby simplifying the seismic retrofitting that will be required. Lowering
the trays also decreases the cost of installing the tray and cables. The
cognizant designer is detailing the new arrangement.
The construction of the new shielding walls in both East and West Pits was started on July 10th. The project included removing existing concrete shielding blocks, modifying the existing metal building siding, excavation, demolition of existing concrete floors and walls, installing a cast in place reinforced concrete wall in each Pit, installing a new entry maze structure at both East and West Pit, and installing new pre-cast roof blocks on the new maze structures and the associated areas with seismic anchors. All the work specified for this shutdown was completed September 22nd on schedule. The installation of the roof shielding blocks and the extension of the reinforced concrete walls in both Pits will be completed during shutdown in FY 2001.
Photos of the shielding work shown below include the East straight section
inner wall (Figure 8.1), east entry maze (Figure 8.2), and west straight
section outer wall with future beam line alcove (Figure 8.3).
Figure 8.1 East Straight Section
Figure 8.2 East Entry Maze
Figure 8.3 West Outer Wall
2.1 Accelerator Physics
During the fourth quarter of FY 2000, efforts of the accelerator physics group were concentrated on software development, specifications for beam diagnostics, beam stability studies and analysis of prototype magnet field measurements. Studies of magnet-to-beam amplification factors were carried out.
The accelerator simulator in MATLAB has been extended to include calculation of particle beam moments including radiation effects. The moment calculations are based on theory developed at KEK (K. Ohmi, Physical Review E, 49, No. 1, 1994) which can be used to compute beam-size, emittance, and damping times in a fully coupled machine with radiation at all components. These calculations, in conjunction with coupled-lattice betatron function calculation based on theory developed at Cornell, will be used to study coupling in SPEAR 2 and SPEAR 3.
The closed-orbit calculation routines have been updated. These calculations now include both 4-D and 6-D computations wioth radiation and rf cavity effects. Depending on the order of approximation required, the software engineer can choose the closed-orbit calculation appropriate for the current study.
Additional work was also carried out to develop first release software for the MATLAB Accelerator Toolbox (AT). The toolbox is being assessed at LBL for possible adaptation to needs at the ALS. As part of an on-going accelerator physics collaboration with the ALS, the Accelerator Toolbox was presented at two seminars at LBL (physics seminar, Light Source Workshop).
Orbit Control Application Program
The Orbit program has been upgraded for file handling capabilities and provided with a save/restore facility. A response-matrix measurement routine has been added to the Orbit Control program. The software group has upgraded the SPEAR Channel Access Server to deliver electron beam orbit data. This paves the way for studies to begin using the MATLAB Orbit Control program on SPEAR. When SPEAR 2 starts up (Nov. 1, 2000) tests of channel access server through MATLAB and the Orbit Control algorithms will commence. The CAMD accelerator in Louisiana has successfully used the program for slow feedback control and the Advanced Light Source at LBL is investigating application to the ALS.
Magnetic Measurements: Tracking Studies
Magnetic measurements are arriving for the prototype dipole and quadrapole articles. Based on the measured mulitpole spectrum, tracking studies were performed to verify performance of non-linear particle dynamics. In particular, the n=6 multipole on the quadrapole was shown to be acceptable but further tests were recommended to reduce the field value. As described in the magnet section of this report, the tests were successfully carried out by the IHEP team and will be integrated into the final end chamfer design for the quadrupole. The multipole spectrum of the prototype dipole magnet is acceptable.
Synchrotron Light Monitor
Studies continue for the synchrotron light monitor system (SML) on SPEAR 3. Two prospect locations for the system were identified: (1) 17S18 straight section and (2) beamline 1. The 17S18 option is preferred because SLM construction would be decoupled from the beamline development program and the vacuum chamber could provide up to 22 mrad horizontal and 2.5 mrad vertical acceptance of the dipole radiation fan. The 17S18 location also provides maximum distance between the source point and the cold finger to moderate the central x-ray power. The drawback to the 17S18 location is complication with locating the optical bench in the ‘y’ formed between SPEAR and the BTS. Continuation of the building extension for the West Pit region to enclose the 17S18 laboratory would be beneficial. The beamline 1 option is limited by a <1.6 mrad vertical acceptance and unpredictable timetable due to coupling to the beamline development program.
Locations for pinhole cameras and physics issues surrounding the use of pinhole cameras on SPEAR 3 are under investigation.
Particle Beam Scraper
In conjunction with the vacuum group, studies have been made to investigate the use of particle beam scrapers in SPEAR 3. To date, we have identified the need for a single horizontal scraper and a top/bottom pair of vertical scrapers for beam-lifetime studies. One of these systems (horizontal or vertical) will also be used for the slow beam abort system during machine studies. An additional, redundant pair of beam stoppers will be used for machine- and personnel-protection. The main difficulty with the scrapers for accelerator physics applications is power loading: if the scrapers are inserted too rapidly, the 1.2kJ energy of a 500 ma beam can be deposited too fast leading to scraper damage. The vacuum group is therefore investigating scraper designs that will permit the most rapid insertion of these devices without leading to scraper damage but with high position resolution for physics studies.
Magnet-to-Beam Amplification Factors
Based on conversations with designers of the Swiss Light Source, we are investigating support of the SPEAR 3 magnet girders on cam-driven movers. The movers would provide girder positioning to an accruacy of tens of microns and the possibility of remote beam-based ring alignment. In addition, if the magnets could be mounted directly on top of the girders (struts removed) the vibrational motion of the magnets would be reduced and the normal modes of oscillation driven to higher frequency. To study the impact on beam stability, amplification factors from magnet-motion to beam-motion were computed for each quadrupole and dipole magnet. The expectation values were then computed for each magnet family (in each plane) and for all magnet families combined. The statistical expectation factors for the magnification were on the order of 30 in the horizontal plane and the order of 25 in the vertical plane. By ganging magnets on respective girders, these values were reduced by approximately a factor of 2. Overall, combining the ground-to-magnet amplification factors with the magnet-to-beam amplification factors for the anticipated ground motion spectrum at SPEAR, coupled with added cost and floor space restrictions, it does not appear necessary to pursue the cam-mover approach for SPEAR 3.