CIRCE, the Proposed Coherent Infrared Center at the LawrenceBerkeley National Laboratory Page: 3 of 7
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In designing the CIRCE ring we have made provisions for optimized versions of all
the above-described techniques for the generation of terahertz CSR. Figure 1 shows a 3D
layout of the CIRCE ring inside the ALS facility. The new ring, 66 m in circumference
and operating at 600 MeV, is designed to be located on top of the ALS Booster Ring
shielding and will share the injector with the ALS storage ring.
Figure 2 shows the impressive flux of CIRCE calculated for three different settings
of the ultra-stable mode of operation. The gain of many orders of magnitude in the
terahertz frequency range over the existing "conventional" source is clearly visible. In
Figure 3, we show how the femtoslicing mode nicely complements the ultra-stable mode
of operation in CIRCE. In fact, the calculated spectra for the two modes together cover
the entire terahertz range from wavelengths of about 10 pm (30 THz) to about 10 mm
(0.03 THz). The energy per THz pulse in the example used for the femtoslicing case is
about 8.5 pJ which when focused onto a sample would provide an electric field of about
106 V/cm. The present laser technology should allow repetition rates as high as 10 + 100
The vacuum chambers in the dipole magnets and the first in-vacuum mirror have
been specially designed for efficient collection of terahertz synchrotron radiation. The
design calls for three ports with 100-mrad horizontal by 140-mrad vertical acceptance for
each of the 12 dipole magnets, giving a potential total of 36 dipole beamlines in CIRCE.
The ring lay-out also includes six 3.5-m straight sections that can be used for insertion
devices for future possible sources (as for the case of the wiggler in the femtoslicing
At the present time, we have completed a detailed feasibility study of CIRCE that
includes electron beam linear and nonlinear dynamics studies, magnetic design of all the
magnets, design of the special high-acceptance dipole vacuum chamber, and evaluation
of the compatibility of CIRCE with the ALS facility. In addition, we have experimentally
investigated the issue of possible resonating modes that could be excited by the electron
beam in the high-acceptance dipole vacuum chamber. These modes, potentially
dangerous for the electron beam stability, have been measured and characterized by
means of radio-frequency measurements in a prototype dipole chamber. No "show
stoppers" have been identified and CIRCE is part of the current five years strategic plan
for the ALS.
For additional information about CIRCE, please visit: http://CIRCE.lbl.gov/.
*LBNL CIRCE TEAM: J. M. Byrd, S. De Santis, J.-Y Jung, S. Kwiastkoski, D. Li, A.
Loftsdottir, S. Marks, Michael C. Martin, D. Munson, H. Nishimura, D. S. Robin,
F. Sannibale, R. Schlueter, W. Thur, M. Venturini, M. Zolotorev.
Work supported by the U.S. Department of Energy under Contract No. DE-AC02-
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Byrd, John M.; Martin, Michael M. & Sannibale, Fernando. CIRCE, the Proposed Coherent Infrared Center at the LawrenceBerkeley National Laboratory, article, July 12, 2005; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc875425/m1/3/: accessed January 18, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.