| BIW 98 Abstracts: TUTORIAL,
INVITED and CONTRIBUTED TALKS MONDAY
MAY 4, MORNING SESSION:
Instrumentation and Diagnostics for PEP-II (invited)
Alan S. Fisher SLAC
PEP-II is a 2.2 km circumference collider with
a 2.1 A, 3.1 GeV positron ring (the Low-Energy
Ring) 1 m above a 1 A, 9 GeV electron ring (the
High-Energy Ring); both rings are designed to
allow an upgrade to 3 A. Since June 1997, we have
had three runs totaling fourteen weeks to
commission the full HER, reaching a current of
0.75 A. Positrons were transported through the
first 90 m of the LER in January 1998, with
full-ring tests planned for the summer. This
workshop provides a timely opportunity to review
the design of the beam diagnostics and their
performance, with an emphasis on what works, what
doesn’t work, and what we’re doing
about it. I will discuss: the synchrotron-light
monitor, including both transverse imaging onto a
CCD camera and longitudinal measurements with a
streak camera; tune measurements with a spectrum
analyzer, with software for peak tracking;
measurements of both the total ring current and
the charge in each bucket, for real-time control
of the fill; beam-position monitors, with
processors capable of 1024-turn records, FFTs,
and phase-advance measurements; and beam-loss
monitors using small Cherenkov detectors for
measuring both stored-beam and injection losses.
Beam Diagnostics and Applications (tutorial)
Albert Hofmann
Particle beams are detected through the
electro-magnetic fields they create. Position
monitors are based on the near-field which stays
attached to the charges. A large number of
measurements can be carried out with such
monitors. By reading out the position, averaged
over many turns, the closed orbit is obtained.
Its change due to a deflection gives the lattice
functions. With a fast position monitor the
betatron tune can be measured. Its dependence on
ener
gy deviation, intensity and quadrupole
strength gives information on chromaticity,
impedance and local beta function.
Having turn by turn reading in all monitors
allows the measurement of beta functions and
phase advances around the ring in order to check
the optics. Diagnostics based on the far-field is
done with synchrotron radiation. It is used to
form an image o
f the beam cross section and to
measure its dimensions. Due to the small natural
opening of the radiation the resolution is
limited by diffraction. The angular spread of the
particles can be measured by direct observation
of the emitted synchrotron radiation.
Electron Beam Parameters Measurements Using
Bremsstrahlung at Electron-Proton Storage Ring (contributed)
Yu.A. Bashmakov , M.S Korbut DESY
At an electron-proton storage ring
electromagnetic interaction of electrons with
counter protons produces bremsstrahlung. Now this
radiation is widely used for collider luminosity
measurement. Bremsstrahlung photons distribution
can be used also for measurement of electron beam
divergence at interaction point. Comparison of
bremsstrahlung angular distribution and electron
beam angular spread is given for energy range
typical for the electron-proton storage ring
HERA. The counter proton beam is a strongly
inhomogeneous target. It makes possible
determination of relative position of electron
and proton bunches at the interaction point in
the transverse plane. Experimental data for
photon and el
ectron hodoscopes of luminosity
monitor of H1 Detector at electron-proton storage
ring HERA were used for electron beam parameters
extraction. There are experimental evidences that
coherent interactions between electron and proton
bunches can essentially change the second
electron angular distribution.
DAFNE Beam Instrumentation (contributed)
A.Ghigo, C
. Biscari, G. DiPirro,
A.Drago, A.Gallo, F.Marcellini, G.Mazzitelli,
C.Milardi, F.Sannibale, M. Serio, A.Stecchi,
A.Stella, G. Vignola, M.Zobov
INFN, Laboratori Nazionali di Frascati
DAFNE, the Frascati Phi-Factory is now under
commissioning. The accelerator complex is
composed by a linac, an accumulator-damping ring
and two separate main rings, one for
electrons
and the other for positrons, with two interaction
regions in which the experiments will be placed.
In order to achieve the luminosity goal, high
performance instrumentation and beam diagnostics
have been installed. Some of the relevant beam
measurements performed are: beam emittance,
transverse and longitudinal dimensions, beam
positions and tunes, overlap in the
interaction
points and luminosity. An overview of the
diagnostic instrumentation of the accelerator
complex is given together with measurement
examples and discussion of operational
experiences.
TUESDAY MAY 5, MORNING SESSION:
Polarimeters and Their Applications
Electron Beam Polarimetry (tutorial)
Charles Sinclair
TJNAF
Along with its well-known mass and charge, the
electron also carries an intrinsic angular
momentum, or "spin". The rules of
quantum mechanics allow us to measure only the
probability that the electron spin is in either
of two allowed spin states. When a beam carries a
net excess of electrons in one of these two
allowed spin states, the beam is said to
be
"polarized". The beam polarization may
be measured by observing a sufficient number of
electrons scattered by a spin-dependent
interaction. For electrons, the useful scattering
processes involve Coulomb scattering by heavy
nuclei, or scattering from either polarized
photons or other polarized electrons (know as
Mott scattering, Compton scattering, and Møller
scattering, respectively). In this tutorial, we
will briefly review how beam polarization is
measured through a general scattering process,
followed by a discussion of how the three
scattering processes above depend on the electron
spin. Detailed descriptions of actual electron
polarimeters based on the three scattering
processes will be given.
Mea
suring The Proton Beam Polarization
Yousef Makdisi BNL
While techniques for measuring the degree of
polarization of polarized proton beams at low
energy are relatively well understood, such is
not the case for energies above 50 GeV. The
experience at the Brookhaven AGS will be
described as will the effort to design
polarimeters for the Polarized Proton Pro
ject at
the BNL Relativistic Heavy Ion Collider (RHIC)
will be discussed. Polarimeter options, design
criteria, kinematic coverage, choice of detectors
and required resolutions, and computer
simulations of the particle densities and rates
the RHIC environment will be described. The
physics program and the funding profile put
certain constraints on the polarimetry at RHIC
and the long-range plan will be presented.
High-Average-Power Proton Beam-Profile
Measurements (invited)
J. D. Gilpatrick LANL
In a collaborative effort with industry and
several national laboratories, the Accelerator
Production of Tritium (APT) and the Spallation
Neutron Source (SNS) facilities are presently
being designed and de
veloped at Los Alamos
National Laboratory (LANL). The APT facility is
planned to accelerate a 100-mA, H+, CW-beam to
1.7 GeV and the SNS facility is planned to
accelerate a 4-mA-average, H-, pulsed-beam to 1
GeV. With typical rms beam widths of 1- to 3-mm
throughout much of these accelerators, the
maximum average-power-densities of these APT and
SNS proton beams is expected
to be approximately
30- and 1-MW-per-square millimeter, respectively.
These power densities are too large to use
standard interceptive techniques typically used
at other facilities for acquisition of beam
profile information. This paper will summarize
the specific requirements for the beam profile
measurements to be used in the APT, SNS, and the
Low Energy Development Acce
lerator (LEDA) - a
facility to verify the operation of the first
20-MeV of APT. This paper will also discuss the
variety of profile measurements choices discussed
at a recent high-average-current beam profile
workshop held in Santa Fe, NM, and will present
the present state of the design for the beam
profile measurements planned for APT,SNS, and
LEDA.
<
p>Real-Time Orbit Feedback at the APS (invited)
John A. Carwardine, Frank Lenkszus APS
The APS is the largest and brightest
third-generation synchrotron light source in the
United States, delivering intense x-rays to as
many as 35 insertion-device and 35 bending-magnet
beamlines. Positional stability of the x-ray beam
is critical to the APS performance, and feedback
is used in order to eliminate orbit drift and to
cancel dynamic orbit motion from sources such as
ground vibration and power supply ripple. This
paper focuses on dynamic orbit stability and
describes the fully digital real-time orbit
feedback system that has been implemented at the
APS. With real-time global orbit feedback
running, orbit motion below 30 Hz is reduced by a
factor of two to about 8 microns rms horizontally
and 2.5 microns rms vertically. Ultimately, the
real-time system will also provide local
source-point control using installed photon BPMs
to measure x-ray beam position and angle
directly. The emphasis of the paper will be on
technical challenges associated with real-time
orbit feedback and the solutions chosen for the
APS system. These include the issues of algorithm
robustness and correct magnet bandwidth. The
unique diagnostic capabilities provided by the
APS real-time system and their use in identifying
sources of orbit motion will also be described.
TUESDAY MAY 5, AFTERNOON SESSION
Laser Diagnostic for High Current H- Beams (contributed)
Robert E. Sha
fer Los Alamos National
Laboratory
In the last 5 years, significant technology
advances have been made in the performance, size,
and cost of solid-state diode-pumped lasers.
These developments enable the use of compact
Q-switched Nd:YAG lasers as a beam diagnostic for
high current H- beams. Because the binding energy
of the last electron is only 0.75 eV, and the
maximum detachment cross section is 4 E-17 cm2 at
1.5 eV, A 50 mJ/pulse Q-switched Nd:YAG laser can
neutralize a significant fraction of the beam in
a single 10-ns wide pulse. The neutral beam
maintains nearly identical parameters as the
parent H- beam, including size, divergence,
energy, energy spread, and phase spread. A dipole
magnet can separate the neutral beam from the
H-beam to allow diagnostics on the neutral beam
without intercepting the high-current H- beam.
Such a laser system can also be used to extract
low current proton beams for cancer therapy
treatment, or induce fluorescence in partially
stripped heavy ion beams. Possible beamline
diagnostic systems will be reviewed, and the
neutral beam yields will be calculated for
several examples.
Linac-Beam Characterizations at 600 MeV
Using Optical Transition Radiation Diagnostics (contributed)
Alex H. Lumpkin, Bingxin Yang, William J.
Berg, Marion White APS
Selected optical diagnostics stations were
upgraded in anticipation of low-emittance, bright
electron beams from a thermionic rf gun or a
photoelectric rf gun
on the Advanced Photon
Source (APS) injector linac. These upgrades
include installation of optical transition
radiation (OTR) screens, transport lines, and
cameras for use in transverse beam size
measurements and longitudinal profile
measurements. Using beam from the standard
thermionic gun, tests were done at 50 MeV and 400
to 650 MeV. Data were obtained on the limiting
spatial (s ~ 200 m m) and temporal resolution
(300 ms) of the Chromox (A12 03
: Cr) screen (250-m m
thick) in comparison to the OTR screens. Both
charge-coupled device (CCD) and charge-injection
device (CID) video cameras were used as well as
the Hamamatsu C5680 synchroscan
streak camera
operating at a vertical deflection rate of 119.0
MHz (the 24th subharmonic of the
S-band 2856 MHz frequency). Beam transverse sizes
as small as s x
= 60 m m for a 600 MeV
beam and micropulse bunch lengths of s t
< 3ps have been
recorded for
macropulse-averaged behavior with changes of
about 2 to 3 nC per macropulse. These techniques
are applicable to linac-driven, fourth-generation
light source R&D experiments including the
APS’s SASE FEL experiment. Results from the
rf gun will be presented as available.
YAG Profile Monitor and Its Applications (contributed)
W.S. Gra
ves, E.D. Johnson, S. Ulc BNL
A new beam diagnostic to measure transverse
profiles of electron beams is described. This
profile monitor uses a Yttrium:Aluminum:Garnet
(YAG) crystal doped with a visible-light
scintillator to produce an image of the tranverse
beam distribution. The advantage of this material
over traditional fluorescent screens is that it
is formed fro
m a single crystal, and therefore
has improved spatial resolution. RMS electron
beam sizes as small as 11 microns have been
measured. The best resolution achievable by the
monitor is approximately 1 micron, limited by the
diffraction of visible light. In addition to high
resolution, the YAG screen is as bright as the
best phosphors and is linear over a wide range of
charge
density.
Two applications of the monitor are described.
One is a high-resolution profile monitor designed
for use in small gap magnetic undulators. This
monitor uses periscope optics and a fixed reticle
to reduce its sensitivity to positioning errors.
The second application is a very compact 3-screen
emittance monitor. An unusual aspect of this
monitor is that the sc
reens are positioned within
another experimental apparatus. This arrangement
provides precise knowledge of beam size, centroid
position, and divergence angle directly where it
is needed.
Beam Diagnostics Based on Time-Domain
Bunch-by-Bunch Data (contributed)
D. Teytelman, J. Fox, H. Hindi, C. Limborg, I.
Linscott, S. Prabhakar, J. Sebek, A. Young,
Stanford Linear Accelerator Center;A. Drago, M.
Serio,. INFN - Laboratori Nazionali di
Frascati;W. Barry, G. Stover, Lawrence Berkeley
National Laboratory
A bunch-by-bunch longitudinal feedback system
has been used to control coupled-bunch
longitudinal motion and study the behavior of the
beam at ALS, SPEAR, PEP-II, and DAFNE. Each of
these machines prese
nts unique challenges to
feedback control of unstable motion and data
analysis. Here we present techniques developed to
adapt the feedback system to operating conditions
at these accelerators. A diverse array of
techniques has been developed to extract
information on different aspects of beam behavior
from the time-domain data captured by the
feedback system. These include
measurements of
growth and damping rates of coupled-bunch modes,
bunch-by-bunch current monitoring, measurements
of bunch-by-bunch synchronous phases and
longitudinal tunes, beam noise spectra. A
technique is presented which uses the synchronous
phase information to compute the machine
impedance as a function of frequency. Techniques
are illustrated with data acquired at al
l of the
four above-mentioned machines.
First 7-GeV Particle Beam Measurements
Using a Synchroscan and Dual-Sweep X-ray Streak
Camera (contributed)
Alex H. Lumpkin, Bingxin Yang APS
Particle-beam characterizations of a 7-GeV
storage ring beam have been done for the first
time using a synchroscan and dual-sweep x-ray
streak camera
at the Advanced Photon Source
(APS). The hard x-rays (5-20 keV) from a bending
magnet source point were imaged using a four-jaw
pinhole aperture. The same camera tube had
previously been tested on a UV laser at 248 nm,
but the flange with a quartz window was replaced
by one with a Be window for these experiments.
The x-ray synchrotron radiation (XSR) was
directly detected
by the Au photocathode of the
streak tube. The Hamamatsu C5680-36 tube’s
vertical deflection (fast time) was driven by a
synchroscan unit tuned to 117.3 MHz (1/3 of the
storage ring rf frequency), and the horizontal
deflection (slow time) was driven by the model
M5679 dual-sweep unit. To provide positioning of
the camera’s 50-microns-tall photocathode
and to allow
spatial and temporal calibrations to
be done, the camera mainframe was mounted on
three stacked translation stages that provided
x-,y-, and z (t)-axis motion. Stored-beam bunch
lengths of 65 to 80 ps (FWHM) or 28-34 ps (s ) were observed with low
jitter and an ~ 4 ps (s
) resolution (a four times faster sweep range is
p
ossible) during users run at ~ 80 mA stored beam
current. Additionally, the horizontal spatial
profile was also obtained simultaneously with a
total observed size of s
x =300 m m
(including aperture effects). The x-ray
wavelengths involved in these test are 1000 times
shorter than UV light so diffraction limits to
spatial resolution can be reduced in some beam
dynamics experiments. Since the tube is sensitive
to 10-eV to 10-keV photons, there is a strong
overlap with the paths envisioned for the R&D
towards 4th-generation light sources
in the soft or hard x-ray regime. The temporal
resolution on the fastest streak range (~ 1 to 2
ps (s )) can address
any storage-ring based source presently
envisioned for the next generation.
WEDNESDAY MAY 6, MORNING SESSION:
Cavity BPMs (tutorial)
Ronald Lorenz DESY Zeuthen
Beam-based alignment and feedback systems are
essential for the operation of future linear
colliders and free-electron lasers. A certain
number of beam p
osition monitors with a
resolution in the submicron range are needed at
selected locations.
Most beam position monitors detect the
electric or the magnetic field excited by a beam
of charged particles at different locations
around the beam pipe. In resonant monitors
however, the excitation of special field
configurations by an off-center beam is detected.
These structures offer a huge signal per micron
displacement.
This paper is an attempt to summarize the
fundamental characteristics of resonant
structures, their advantages and trade-offs.
Emphasis will be on the design of cylindrical
cavities, in particular on the estimation of
expected signals, of resolution limits and the
resulting beam distortion. This incl
udes also a
short introduction into numerical methods.
Fabrication, tuning and other practical problems
will be reviewed briefly. Finally, some resonant
devices used for beam position diagnostics and
their performance will be listed.
RHIC Instrumentation (invited)
T. J. Shea, R. L. Witkover BNL
The Relativistic Heavy Ion Collider (RHIC)
consists of two 3.8 km circumference rings
utilizing 396 superconducting dipoles and 492
superconducting quadrupoles. Each ring will
accelerate approximately 60 bunches of 10^11
protons to 250 GeV, or 10^9 fully stripped gold
ions to 100 GeV/nucleon. Commissioning is
scheduled for early 1999 with detectors for some
of the 6 intersection regions scheduled for
initial
operation later in the year. The
injection line instrumentation includes: 56 Beam
Position Monitor (BPM) channels, 56 Beam Loss
Monitor (BLM) channels, 4 fast integrating
current transformers and 12 video beam profile
monitors. The Collider Ring instrumentation
includes: 667 BPM channels, 400 BLM channels,
wall current monitors, DC current transformers,
ionization profile
monitors (IPMs), transverse
feedback systems, and resonant Schottky monitors.
The use of superconducting magnets affected the
beam instrumentation design. The BPM electrodes
must function in a cryogenic environment and the
BLM system must prevent magnet quenches from
either fast or slow losses with widely different
rates. RHIC is the first superconducting
accelerator to cro
ss transition, requiring close
monitoring of beam parameters at this time. High
space charge due to the fully stripped gold ions
required the IPM to collect magnetically guided
electrons rather than the conventional ions.
Since polarized beams will also be accelerated in
RHIC, additional constraints were put on the
instrumentation. The orbit must be well
controlled to minim
ize depolarizing resonance
strengths. Also, the position monitors must
accommodate large orbit displacements within the
Siberian snakes and spin rotators. The design of
the instrumentation will be presented along with
results obtained during bench tests, the
injection line commissioning, and the first
sextant test.
Characterizing Transverse Beam Dynamics at
the APS Storage Ring Using a Dual-Sweep Streak
Camera (contributed)
Bingxin Yang, Alex H. Lumpkin, Katherine
Harkay, Louis Emery, Michael Borland, Frank
Lenkszus APS
We present a novel technique for
characterizing transverse beam dynamics using a
dual-sweep streak camera. The camera is used to
record the front view of successive beam bunches
and/or successive turns of the bunches. This
extension of the dual sweep technique makes it
possible to display non-repeatable transverse
beam motion in two fast and slow time scales of
choice, and in a single shot. We present a study
of a transverse multibunch instability when the
APS storage ring is filled with a long bunch
train. The positions, sizes, and shapes of the 20
bunches (2.84 ns apart) in the train, in 3 to 8
successive turns (3.6 microseconds apart) are
recorded in a single image, providing rich
information about the unstable beam. This
includes the amplitude of the oscillation (~0.0
at the head of the train and ~0.5 mm toward the
end of the train), the bunch-to-bunch phase
difference, and the significant transverse size
growth within the train. In the second example,
the technique is used to characterize the
injection-kicker-induced beam motion, in support
of the planned storage ring top-up operation. By
adjusting the time scale of the dual sweep, it
clearly shows the amplitude (~1.8 mm) and
direction of the kick, and the subsequent
decoherence (~ 100 turns) and damping (~20 ms) of
the stored beam. Since the storage ring has an
insertion device chamber with full vertical
aperture of 5 mm, it is of special interest to
track the vertical motion of the beam. An
intensified gated camera was used for this
purpose. The turn-by-turn x-y motion of a
single-bunch beam with coupling uncorrected was
recorded. A video recording of the kickers
magnets effects on
the stored beam will also be
presented.
Fundamental Limits on Beam Stability at the
Advanced Photon Source (contributed)
Glenn A. Decker, John A. Carwardine, Om V.
Singh APS
Orbit correction is now routinely performed at
the few-micron level in the Advanced Photon
Source (APS) storage ring. Three diagnostics are
presently in use
to control both AC and DC orbit
motions: broad-band turn-by-turn rf beam position
monitors, narrow-band switched heterodyne
receivers, and photoemission-style x-ray beam
position monitors. Each type of diagnostic has
its own set of systematic error effects that
places limits on the ultimate pointing stability
of x-ray beams supplied to users at the APS.
Limiting sources of
beam motion at present are
magnet power supply noise, girder vibration, and
thermal timescale vacuum chamber and girder
motion. This paper will investigate the present
limitations on orbit correction and will delve
into the upgrades necessary to achieve true
submicron beam stability.
Alignment Measurement of an X-Band
Accelerator Structure Using Beam Induced Dipol
e
Signals (contributed)
Chris Adolphsen SLAC
Precise beam-to-structure alignment is
critical for the acceleration of small emittance
beams in linear accelerators. For the Next Linear
Collider (NLC), a prototype accelerator structure
has been developed in which the beam induced
dipole mode signals can be readily accessed and
processed to ex
tract alignment information. In a
test in the SLC linac, we used these signals to
measure the internal alignment of the structure
and to steer the beam in an attempt to minimize
its wakefield. We used a second bunch to directly
measure the wakefield and inferred from the
results that a better than 40 micron alignment
had been achieved. In this paper, we review these
results
and describe how we want to implement
this alignment scheme for the approximately ten
thousand structures in the NLC.
WEDNESDAY MAY 6, AFTERNOON SESSION:
From Narrow to Wide Band Normalization for
Orbit and Trajectory Measurements (contributed)
G. Vismara, D. Cocq CERN
The beam orbit measurement of the LEP collider
makes use of a narrow band normalizer (NBN) based
on a phase processing system of the output burst
signal from a band-pass filter. This design has
been working fully satisfactory in LEP for almost
10 years. Development work for the LHC, requiring
beam acquisitions every 25 ns, has led to a new
idea of a so called "wide band
normaliser" (WBN) which exploits most of the
P.U.’s differentiated pulse spectrum. In the
WBN the beam position information is converted
into a time difference between the zero crossing
of two recombined and shaped electrode signals.A
prototype based on the existing NBN unit has been
developed and tested to prove the feasibility of
this new idea. For this the B.P. filters and the
90° hybrids are replaced by L.P. fil
ters and
delay lines. After describing the basic
principles, the paper gives details on all blocks
of the WBN processing chain and the measurement
results obtained by the prototype are presented.
The paper gives sufficient information for
instrumentation experts and electronics engineers
who want to understand and further exploit the
large potential of this system.
Improvement of the Noise Figure of the
CEBAF Switched Electrode Electronics BPM System (contributed)
Tom Powers Thomas Jefferson National
Accelerator Facility
The Continuous Electron Beam Accelerator
Facility (CEBAF) is a high-intensity continuous
wave electron accelerator for nuclear physics
located at Thomas Jefferson National Accelerator
Facility. A beam energy of 4 GeV is achieved by
recirculating the electron beam five times
through two anti-parallel 400 MeV linacs. In the
linacs, where there is recirculated beam, the BPM
specifications must be met for beam intensities
between 1 and 1000 m
A. In the transport lines the BPM specifications
must be met for beam intensities between 100 nA
and 200 m A. To avoid
a complete redesign of the existing electronics,
we investigated ways to improve the noise figure
of the Linac BPM switched electrode electronics
(SEE) so that they could be used in the transport
lines. We found that the out-of-band noise
contributed significantly to the overall system
noise figure. This paper will focus on the so
urce
of the excessive out-of-band noise and how it was
reduced. The development, commissioning and
operational results of this low noise variant of
the linac style SEE BPMs as well as techniques
for determining the noise figure of the RF chain
will also be presented.
Studies of Beam Position Monitor Stability (contributed)
P. Tenenbaum SLAC
We present the results from two studies of the
time stability between the mechanical center of a
beam position monitor and its
electrical/electronic center. In the first study,
a group of 93 BPM processors was calibrated via
Test Pulse Generator once per hour in order to
measure the contribution of the readout
electronics to the offset drifts. In the second
stud
y, a triplet of stripline BPMs in the Final
Focus Test Beam, separated only by drift spaces,
was read out every 6 minutes during 1 week of
beam operation. In both cases offset stability
was observed to be on the order of microns over
time spans ranging from hours to days, although
during the beam study much worse performance was
also observed. Implications for the beam position
monitor system of future linear colliders are
discussed.
Experiences of the QSBPM system on MAX-II (contributed)
Peter Röjsel MAX-lab, Lund University
The MAX-II is a third generation synchrotron
radiation source. The first beamline is in
operation and several others are in comissioning.
The storage ring is equipped with a QSBPM system
for c
alibration of the button pickup BPM system
in situ. The calibration system uses switchable
shunts on the combined function
quadrupole-sextupole magnets to find their
magnetic centra. The BPM system has a long time
constant of several seconds so a switched system
is the only alternative. Each BPM pickup and its
corresponding electronics has been calibrated
with the QSBPM sys
tem. The system has now been in
operation for about two years and operational
experiences together with the technique itself
and the impact on machine performance is
discussed.
The quadrupole shunts that is a part of the
QSBPM system is together with a spectrum analyzer
and a tracking generator also used to measure the
beta functions individually in all quadrupoles
of
the machine.
THURSDAY MAY 7, MORNING SESSION:
Camera Technology and Image Processing
(tutorial)
Roland Jung CERN
Beam monitors using cameras have evolved from
qualitative beam observation to precision
measurements. After a short description of the
two main TV standards, the various sensors: TV
tubes (Vidicon), solid state sensors (Interline
and Frame Transfer CCDs, cmos and CID X-Y
matrices), and Fast Shutter/Intensifiers of the
MCP type are reviewed. Comparative resolution
measurements for the various sensors described
are given. The two types of sensor acquisition
hardware: "frame grabbers" and
"digital cameras", are described.
Finally
the special requirements and the data
processing of image sensors for beam
instrumentation are reviewed: radiation hardness,
spectral sensitivity, fast acquisitions and
enlarged dynamic range.
Measurement of Chromaticity via Head-Tail
Phase Shift (contributed)
H. Schmickler, D. Cocq, O.R. Jones CERN
The most common method of measuring the
chromaticities of a circular machine is to
measure the betatron tune as a function of the
machine energy and then calculating the
chromaticity from the slope of the measurements.
Even as a simple difference method between two
machine energies, this method does not allow
instantaneous measurements for instance during
energy ramping or beta squeezing. In preparation
for the LHC a new approach has been developed
which uses the energy spread in the beams for a
chromaticity measurement. Transverse oscillations
are excited with a single kick and the
chromaticity is measured from the phase
difference of the individually sampled head and
tail motions of the beam. This way a measurement
can be made during one synchrotron period (about
15-50
msec in the case of the LHC). This paper
describes computer simulations of the
measurements, two different experimental set-ups
and measurements made in the SPS.
Faraday Cup Speaker
(To Be Announced).
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