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In this issue:
LCLS Beam Already in Action
Dorfan Today: The LCLS Forges Ahead
SPEAR3 Annual Shutdown Begins Today
Safety Firsts

SLAC Today

Monday - August 6, 2007

The LCLS beam is already being used by experimentalists at End Station A.
(Click on image for larger version.)

LCLS Beam Already in Action

The Near and Far Experimental halls are still under construction, but already scientists are putting the Linac Coherent Light Source (LCLS) beam to use. The LCLS electron beam, first generated in April, is now traveling from its source near Sector 20, through the Beam Switchyard at the end of the linear accelerator and into End Station A, one of SLAC's original experimental halls.

The one-kilometer journey not only helps the LCLS team commission components along the route, but the beam is already proving useful to scientists working on a diverse set of experiments in End Station A.

In early July, the beam was first pressed into service to help set up a suite of International Linear Collider (ILC) experiments coordinated by Mike Woods. The ILC research is to develop beam instrumentation and to characterize wakefield effects that degrade beam quality. During setup, the ILC experimenters were able to provide diagnostics for the charge, energy spread and jitter of the LCLS beam.  Read more...

(Director's Column - Dorfan Today)

Over the last several months I've had the recurring privilege of sharing news of successes related to the Linac Coherent Light Source (LCLS). The recent tunneling breakthrough was only the most recent visible affirmation of how rapidly the LCLS is taking shape.

I am happy to report that, as of this past month, even in the early stages of commissioning, the LCLS beam is already producing science. It's great to follow what has been the seemingly relentless march of the LCLS beam—from the initial pulse of electrons last April, through the magnetic chicanes, and into the final sections of the linac. Importantly, however, this past month, the LCLS beam was successfully transported into the Beam Switch Yard at the design energy of 13.6 GeV. This means the commissioning and operations group has brought the beam as far east as it can go within the present accelerator housing. This achievement is paying dividends even outside of the LCLS group, and is proving useful to several experimental groups working in End Station A (ESA). Today's lead story offers a more complete account of the experiments underway.

A diversity of groups have already put the LCLS beam to use, and they, in turn, are able to give back to the LCLS project. Partnering with the LCLS commissioning team, SLAC physicists conducting International Linear Collider (ILC) research have helped the LCLS team to cross check measurements of beam charge. The ILC experimenters, accelerator operators and the LCLS Controls group found that a particular diagnostic method was underestimating charge by 45 percent. The newly calibrated measurements, using a different diagnostic technique, reveal that the LCLS injector is meeting its goal of six billion electrons in a 1-micron-emittance bunch. This coming month, members of SLAC's BaBar collaboration will test a prototype particle identification device in End Station A that could further the development of detector technologies for use in future Super-B Factories.

The LCLS team itself is using the beam in experiments that are complementary to the actual process of commissioning. The beam is presently helping establish the upper limits of radiation exposure that the primary LCLS undulator magnets can withstand.

The LCLS is a product of decades of advancement in accelerator research, conducted right here at SLAC. This most recent suite of interdisciplinary successes is all part of what makes SLAC a great laboratory. Our people have the training and access to the facilities to break the boundaries that demarcate traditional fields of science.

SPEAR3 Annual Shutdown Begins Today

Today marks the beginning of the annual SPEAR3 shutdown at the Stanford Synchrotron Radiation Laboratory (SSRL). Each year for three months the storage ring is powered down to accommodate scheduled maintenance and upgrades, and this year the schedule will be as busy as ever. SPEAR3's injector will continue to run until Thursday, August 9, as work continues on the new photocathode injector gun. The lab will resume operation in late October.

Several maintenance and upgrade activities are on the docket for the injector during the shutdown. The primary activity will be the replacement of most of the booster-to-SPEAR (BTS) transport line which carries new beam from the injector to the storage ring during current refills. The goal is to remove several thin windows in the transport line that segregate the very rough vacuum in the majority of the BTS from the high vacuum in both the booster and in SPEAR, and from in-air sections that presently contain insertable screens. This BTS configuration dates back to the very beginning of SPEAR operations in the early 1970s, when SPEAR was filled using the SLAC linac.

The main shutdown tasks for SPEAR include installing a new Beamline 13; moving the Beamline 4 insertion device to a new location to facilitate speedy construction of a new 500 mA-ready beam line during the next user run; further work preparing for top-off injection; and seismic retrofitting of SSRL Building 120 and booster shielding blocks inside injector Building 140.

Beamline 13 will be equipped with an elliptically polarized undulator temporarily taken from the present Beamline 5, which will ultimately be replaced with a new high-performance device during the 2008 shutdown. New components will be installed in the tunnel and on the experimental floor for both Beamline 13 and the relocated Beamline 4. Safety interlock components for top-off injection will be installed for several magnet power supplies, stored beam detectors, and booster extraction energy detectors.

In addition to the large shutdown projects, myriad smaller tasks will also be undertaken. These include an internal inspection of one of the SPEAR radio frequency (RF) cavities, removal of an old high-voltage RF power supply left over from SPEAR2, an upgrade of cooling water and pneumatics systems, replacement of electrical distribution components, installation of additional radiation shielding in the linac, and several modifications and repairs to the beam line liquid-nitrogen monochromator systems.

Safety Firsts

It would seem at first glance that medical errors have nothing to do with the kinds of injuries that we see at SLAC. A patient must in general trust the medical system, because the complexity and sophistication of diagnosis and treatment in medicine is way beyond what the average person knows, and of course sometimes the patient is not even conscious. Yet the advice given to the average patient in order to avoid a medical error is identical to what we have told the SLAC staff to do to avoid an injury here.

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