Previous Editions__________________________________________________________________________SSRL Headlines Vol. 10, No. 1 July, 2009__________________________________________________________________________
Contents of this Issue:
Users arriving at SSRL on Wednesday, July 29, found beam lines operating at 200
mA, or twice the previously normal operating current, with a concomitant
two-fold increase in photon flux and brightness. This development, coupled with
the recent initiation of top-off operations, represent major milestones in
realizing the full potential of the SPEAR3 source. These two milestones are the
tangible manifestations of the efforts of a large group of SSRL staff working
in collaboration with the SLAC Radiation Protection Department and the DOE Site
Office. In particular, each of these developments followed extensive careful
studies and reviews of the radiation safety aspects of these performance
envelope enhancements as well as field commissioning studies of the operating
systems. The last of these radiological commissioning studies was completed
successfully Tuesday evening about 12 hours before delivering the first 200-mA
beam to users.
SSRL will operate at 200 mA for the remainder of the FY09 run which will
provide staff and users alike the opportunity to assess the performance of the
beam line optics under the increased power loading of 200 mA operations as well
as detector and experimental instrumentation performance with the two-fold
higher brightness and flux. During the scheduled summer shutdown a new beam
line beam containment system will be installed on each beam line and the beam
lines reviewed for full 500-mA operations. Following the summer down, SPEAR3
will continue to deliver 200 mA beam in the fall, while conducting 500-mA
radiological commissioning activities during selected accelerator physics
shifts. Successful completion of this program is anticipated by January,
resulting in authorization of greater than 200-mA user operations. Concurrent
with this effort, some accelerator physics shifts will be devoted to
understanding the impact of frequent fills (i.e., possibly as frequent as every
ten minutes) on data quality. Based on this experience in early 2010, SSRL will
raise the SPEAR3 current and injection frequency in a systematic program
designed to increase the SSRL brightness and flux while preserving stored
current and photon beam stability, user data quality, and facility safety.
The most common organic solar cell implementation has a polymer/fullerene
bulk-heterojunction (BHJ) blend as the active (sunlight absorbing) layer. To
form the BHJ, the polymer and fullerene (a buckyball) are blended and typically
spontaneously self-assemble into the BHJ. It has remained a puzzle, however,
why some polymerfullerene systems reach optimal efficiency at equal parts
polymer and fullerene and other systems optimize at around 80% fullerene
content.
To understand what causes this variation in efficiencies depending on the
polymer molecule, scientists from SLAC and Stanford used Beam Lines 11-3, 2-1,
and 7-2 for x-ray diffraction experiments to explore the materials at a
molecular scale. They found that for some polymers the fullerene molecules
intercalated (or co-crystallized) within the crystalline structure of the
polymer provided there was enough space within the polymer. This was
surprising, since the researchers were expecting to find two separate
materials: the pure polymer and pure fullerene. The researchers found only the
intercalated phase for BHJs made with equal parts polymer and fullerene.
However, when the polymer:fullerene ratio was 1:4, two phases did form; one was
the polymer-fullerene co-crystal and the other was pure fullerene. These
results fully explain the dependence of efficiency on polymer:fullerene blend
ratio.
This study is the first to find fullerene molecules intercalated within a
polymer crystal. How this co-crystallization affects efficiency and whether it
is a desirable trait remains to be seen. This and future knowledge gained from
analyzing the structure of these materials will allow researchers to understand
the reasons for the diverse behavior of different materials and to design more
efficient materials. This work was published in the journal Advanced
Functional Materials.
Organic semiconductors have the properties of silicon-based semiconductors,
found ubiquitously in the diodes, transistors, and chips that run our modern,
computerized devises, but they are made from organic materials. They have the
potential to be far less expensive to make than the classic silicon versions
and can be made flexible and lighter weight over large areas. One of the most
popular type of organic semiconductor is made from thin films of pentacene, a
long, polycyclic aromatic hydrocarbon molecule. In this form, electrical
current flows primarily through the first few layers of the pentacene material.
A research group led by Zhenan Bao of Stanford University collaborating with
SSRL scientists Stefan Mannsfeld and Michael Toney has used Beam Line 11-3 to
investigate the structure and properties of single molecular layers of
pentacene. Using grazing incidence X-ray diffraction (GIXD) and newly developed
modeling tools, they determined for the first time the precise structural
arrangement and the orientation of the molecules from the weakly-diffracting
films.
The researchers discovered that the molecules stand upright on the substrate
plane. Looking down at the plane, the molecules pack in a herringbone pattern.
They calculated that this orientation of pentacene leads to the material's
electronic properties, which exceed those of single crystalline pentacene. This
research demonstrates that determination of the structural properties of a
single layer of organic semiconductor molecules is possible and that this
information can yield valuable insight into the function of these molecules.
This work was published in the March issue of the journal Advanced
Materials.
The Department of Energy has awarded $4.8 million in Single Individual and
Small Group Research (SISGR) grants to the Stanford Institute for Materials and
Energy Science (SIMES) and the Stanford Synchrotron Radiation Lightsource
(SSRL) for building a new photoemission branch line at SSRL. This new branch
line will be located at current Beam Line 5 next to the existing branch line
5-4. Featuring an elliptically polarized undulator (EPU) and a plane grating
monochromator (PGM), this new branch line will complement the normal incidence
monochromator (NIM) branch line with extended photon energy range (up to 150
eV) and full polarization control. Such a combination of NIM and PGM branch
lines will allow the optimization of each branch line for different type of
experiments. While the NIM branch line is optimized for ultrahigh resolution
ARPES experiments in relatively low photon energy, the PGM branch-line will be
optimized for high photon flux, wider photon energy range with added capability
of performing spin-resolved photoemission studies. Users will have the
flexibility in choosing either branch lines for their scheduled beamtime. It
will take approximately three years to complete the beam line construction work
and the commissioning of the new branch line is expected to start in late 2012.
For information on other photon science-related projects funded under the SISGR
grant program see 7/27/2009 SLAC Today article
The current run year ends and we shut down for maintenance/upgrades on Monday,
August 10 at 6 am. The next run will begin in late October, and the 2009-10
SPEAR operating schedule, which includes information on scheduled maintenance
and accelerator physics studies, is available on the SSRL website.
If you are interested in requesting beam time on X-ray/VUV beam lines for the
first scheduling period for the 2010 run (~late October through early February
2010), submit your request(s) before August 1; submit Macromolecular
Crystallography requests by September 15.
Submit beam time requests by logging into the SSRL User Portal at:
Enter your email address and your password or click on 'request a password'. We
have tried to make the process to submit requests easier by adding a feature
that allows you to clone (copy) a previous request. With the new system, you
also have the ability to save a draft so that you can edit, complete or delete
it at a later date - as long as it is completed by the deadline. Remember to
submit a SEPARATE request for each proposal, beam line, equipment configuration
and/or each individual beam time period requested. If you select a beam line
that has multiple crystal options, you will be prompted to indicate the crystal
you need for your first and second choice beam line(s). If the availability you
indicate on your beam time request changes, please let us know immediately.
Register today to participate in the Annual LCLS/SSRL Users' Meeting and
Workshops, October 18-21, 2009. The annual conference is a great opportunity to
learn about the latest plans, new developments, and user research as well as to
interact with other scientists, potential colleagues, and vendors of light
source related products and services.
http://www-conf.slac.stanford.edu/ssrl-lcls/2009/default.asp
The event kicks off on October 18 with a special symposium celebrating 35 years
of outstanding science at the Stanford Synchrotron Radiation Lightsource. In
addition to reviewing technical accomplishments and research highlights, future
scientific and technical opportunities for SSRL will be discussed.
LCLS/SSRL 2009 officially begins on October 19 with a joint plenary session
featuring updates from SLAC and DOE, a preview of the workshops, a user science
poster session, and a keynote presentation. The Spicer Young Investigator
Award, Klein Professional Development Award, Lytle Award, and the Outstanding
Student Poster Session Awards will be presented on this day. Submit abstracts
for the user poster session by September 5 at:
On October 20, separate concurrent sessions will focus on SSRL and LCLS
facility development, instrumentation, and user science, followed by meetings
of the respective SSRL and LCLS Users' Organizations.
On October 21, several concurrent workshops will be held including
Microimaging; Nanoscale Imaging with the SSRL STXM; Macromolecular
Crystallography; Soft X-ray Beam Line Experiment Preparation; and X-ray Pump
Probe Experiment Preparation.
Please take a few moments to consider nominating your colleagues or students
for one or more of the following awards which will be presented at the Joint
SSRL and LCLS Users' Meeting, October 18-21, 2009:
William E. and Diane M. Spicer Young Investigator Award
—due August 1
Melvin
P. Klein Professional Development Award —due August 1
Farrel
W. Lytle Award —due August 15
We invite you to share your research during the Poster Session (October 19) of
the Annual Users' Meeting. Students, in particular, are encouraged to present
posters and compete for prizes, which include a certificate and a $100 award.
Representatives of the SSRL Users' Organization will judge student posters
during the poster session, and prizes for outstanding posters will be presented
during the meeting. In addition to the reduced student registration fee,
students presenting posters also receive a free dinner - just sign up and
indicate this when you register, see instructions at:
Register at:
Submit abstracts for the user poster session by September 5 at:
The 2009 SMB Summer School will focus on the use and application of X-ray
Absorption Spectroscopy, Macromolecular Crystallography and Small Angle X-ray
Scattering. Invited lectures from experts in these fields will be at the
graduate student/post-doctoral level, but will also be appropriate for
experienced researchers with expertise in one technique and an interest in
learning other techniques to further the scope of their research. The four-day
summer school will feature two days of lectures covering theoretical and
experimental aspects, and two days of hands on training in data analysis. The
afternoon of the last day will be reserved for question-and-answer sessions
hosted by the co-chairs, which will be aimed at addressing specific queries
from the participants.
Co-chairs for the 2009 SMB Summer School are SSRL Staff Scientists Ritimukta
Sarangi (ritis@slac.stanford.edu), Clyde Smith (csmith@slac.stanford.edu) and
Thomas Weiss (weiss@slac.stanford.edu). Funding for the SMB Summer School
program is provided by NIH-NCRR and DOE-BER.
Apply at: http://www-conf.slac.stanford.edu/smb-ss/2009/
As you may be aware from accounts of the incident in the news media, a very
serious act of vandalism was committed on BL1-5 at SSRL over the weekend of
July 17-19. During this isolated event, a large number of samples belonging to
the Joint Center for Structural Genomics were intentionally removed from their
storage dewars and thus destroyed.
SLAC management took this action very seriously resulting in a rapid response
by authorities. As a result of this vigorous investigation, SLAC Director
Persis Drell announced to staff earlier this week that Federal authorities had
made an arrest in the case and the suspect taken into custody. She expressed
her thanks to the DOE Inspector General, DOE Site Office, FBI, San Mateo County
Sheriff's Office, Stanford University Department of Public Safety and SLAC
Security for their thorough investigation and for bringing this case to a rapid
conclusion.
See also: Persis Drell's 7/31/09 SLAC Today communication discouraging
tailgating through security gates at: http://today.slac.stanford.edu/a/2009/07-31.htm
Use the new User Portal to view your allocated beam time and submit an End of
Run Summary after each scheduled experiment. Comments on your experience at
SSRL are extremely important to us as we strive to provide outstanding customer
service on a continuing basis. In addition, your input allows us to meet our
mission requirements, including assessment and reporting. Thank you for your
feedback.
https://www-ssrl.slac.stanford.edu/URAWI/Login.html
__________________________________________________________________________
SSRL Headlines is published electronically monthly to inform SSRL users,
sponsors and other interested people about happenings at SSRL. SSRL is a
national synchrotron user facility operated by Stanford University for the
U.S. Department of Energy Office of Basic Energy
Sciences. Additional support for
the structural biology program is provided by
the DOE
Office of Biological and Environmental Research, the NIH
National Center for Research Resources and the NIH Institute for General Medical
Sciences. Additional information about
SSRL and its operation and schedules is available from the SSRL WWW
site.
__________________________________________________________________________
To leave the SSRL-HEADLINES distribution, send email as shown below:
To: LISTSERV@SSRL.SLAC.STANFORD.EDU
Subject: (blank, or anything you like)
The message body should read
SIGNOFF SSRL-HEADLINES
That's all it takes. (If we have an old email address for you that is
forwarded to your current address, the system may not recognize who
should be unsubscribed. In that case please write to
ssrl-headlines-request@ssrl.slac.stanford.edu and we'll try to figure out
who you are so that you can be unsubscribed.)
If a colleague would like to subscribe to the list, he or she should send
To: LISTSERV@SSRL.SLAC.STANFORD.EDU and use the message body
SUBSCRIBE SSRL-HEADLINES
SSRL Welcome
Page | Science Highlights | Beam Lines |
User Admin | News & Events |
Safety
|
