JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
Since the start of the beam commissioning on October 2007, we have succeeded to increase the beam power of the Rapid Cycling Synchrotron (RCS) in the Japan Proton Accelerator Research Complex (J-PARC). The effect of the high power beam on the vacuum had become visible above the beam power of 50 kW. When the high power beam was operated at 25 Hz, the vacuum pressure became higher. Especially the vacuum of the injection area became worse than other areas. The residual gas analyzer was installed in order to investigate which kinds of outgassing were desorbed by the high power beam. The carbon compound mainly increased with the high power beam in the area. The source of the ougtassing is thought to be carbon foils for charge exchange and/or a electron catcher which was installed in order to collect the stripped electron by the carbon foil. After this, the RCS forwards into the stage where the high power beam is continuously operated during a few weeks. We will report the results of the conditioning effect on the vacuum by the beam itself.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
LASTI, Hyogo
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
KEK, Ibaraki
J-PARC, KEK & JAEA, Ibaraki-ken
The beam commissioning of the J-PARC 3-GeV RCS started in October 2007. The initial machine parameter tuning and underlying beam studies were completed in February 2008 through various beam dynamics measurements, such as optical functions, turn-by-turn beam positions, and transverse and logitudinal beam profiles. Now the RCS is in transition from the first commissioning phase to the next challenging stage and our efforts hereafter will be focused on higher beam power operations. In this paper, we describe experimental results obtained in the high intensity demonstrations in October 2008, together with the corresponding simulation results.
KEK, Ibaraki
The titanium nitride (TiN) coating inside a beam duct has been recently attracting attention as a measure to mitigate the electron cloud effect in positron/proton rings. Here studied is the gas desorption from the TiN-coated copper beam duct, which will be adopted in the upgrade of KEK B-factory (KEKB). In the experiment, the pressure in a TiN-coated duct was measured and compared with that in a non-coated one. The TiN film (200 nm thick) was coated by DC magnetron sputtering at KEK. After an air exposure for the previously-determined period, the duct was evacuated by a turbo-molecular pump (300 l/s). At 50 hours after evacuation, the pressure was about 4 times larger than that for the case of the non-coated one. The residual gas was mainly water. In order to fine the minimum baking temperature to decrease the gas desorption from the TiN coating, the pressures were measured after the baking by changing the temperatures in the practical range, from 50 to 150 degrees. The pressure after the baking at 80 degrees was finally found to be comparable to that for the non-coated one. This paper describes these results in detail including the measurements of gas desorption rates.
CLASSE, Ithaca, New York
LBNL, Berkeley, California
KEK, Ibaraki
SLAC, Menlo Park, California
Funding: Work supported by the National Science Foundation, the US Department of Energy, and the Japan/US Cooperation Program
Wiggler magnets are one of the key components in the ILC Damping Ring. It is critical to the ILCDR GDE to understand electron cloud (EC) growth and patterns, and to develop EC suppression techniques in the wiggler beampipes. The CESR-c superconducting wigglers, closely matching the parameters of the ILCDR wigglers, serve as unique testing vehicles. As part of the CesrTA project, we replaced the copper beampipes of two SCWs with EC diagnostic beampipes, where one of the beampipes is uncoated and the second is coated with a thin TiN film. Each of the EC diagnostic beampipes is equipped with three retarding field analyzers (RFAs) at strategic longitudinal locations in the wiggler field. Each of the RFAs has 12-fold segmentation to measure the horizontal EC density distribution. To maintain sufficient vertical beam aperture and to fit within the SCW warm bore, a thin style of RFA (with a thickness of 2.5 mm) has been developed and deployed. These SCWs with RFA-equipped beampipe have been installed and successfully operated in the re-configured CesrTA vacuum system. This paper describes the design and the construction of the RFA-equipped SCW beampipes and operational experience.
KEK, Ibaraki
CLASSE, Ithaca, New York
UH, Honolulu, HI
Funding: Work supported in part by the US-Japan Cooperation Program
We are working on the development of a high-speed x-ray beam profile monitor for high-resolution and fast response for beam profile measurements to be used at CesrTA and SuperKEKB*. The optics for the monitor are based on a technique borrowed from x-ray astronomy, coded-aperture imaging, which should permit broad-spectrum, low-distortion measurements to maximize the observable photon flux per bunch. Coupled with a high-speed digitizer system, the goal is to make turn-by-turn, bunch-by-bunch beam profile measurements. Following initial tests with a low-resolution mask at large beam sizes (vertical size ~200 um), a high-resolution mask has been made for use with low-emittance beams (vertical size ~10 um) at CesrTA. The first performance results of the high-resolution mask on the low-emittance CesrTA beam are presented.
*J.W. Flanagan et al., Proc. EPAC08, Genoa, {10}29 (2008).
CLASSE, Ithaca, New York
LBNL, Berkeley, California
ANL, Argonne
KEK, Ibaraki
SLAC, Menlo Park, California
Funding: Supported by the US National Science Foundation, the US Department of Energy under Contracts No. DE-AC02-06CH11357, DE-AC02-05CH11231, and DE-AC02-76SF00515, and by the Japan/US Cooperation Program.
CESR at Cornell has been operating as a damping ring test accelerator (CesrTA) with beam parameters approaching those anticipated for the ILC damping rings. A core component of the research program is to fully understand electron cloud effects in CesrTA. As a local probe of the electron cloud, several segmented retarding field analyzers (RFAs) have been installed in CesrTA in dipole, drift and wiggler regions. Using these RFAs, the energy spectrum of the time-average electron cloud current density striking the walls has been measured for a variety of bunch train patterns; with bunch populations up to 2x1010 per bunch, beam energies from 2 to 5 GeV, horizontal geometric emittances from roughly 10 to 133 nm, and bunch lengths of about 1 cm; and for both positron and electron beams. The effect of mitigation measures, such as coatings, has also been studied. This paper will compare these measurements with the predictions of simulation programs, and discuss the implications of these comparisons for our understanding of the physics of electron cloud generation and mitigation in ILC-like damping rings.
CLASSE, Ithaca, New York
LBNL, Berkeley, California
KEK, Ibaraki
ANL, Argonne
Fermilab, Batavia
CalPoly, San Luis Obispo, CA
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
SLAC, Menlo Park, California
Cornell University, Ithaca, New York
Cockcroft Institute, Warrington, Cheshire
Funding: Support provided by the US National Science Foundation, the US Department of Energy, and the Japan/US Cooperation Program.
In March of 2008, the Cornell Electron Storage Ring (CESR) concluded twenty eight years of colliding beam operations for the CLEO high energy physics experiment. We have reconfigured CESR as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D. The primary goals of the CesrTA program are to achieve a beam emittance approaching that of the ILC Damping Rings with a positron beam, to investigate the interaction of the electron cloud with both low emittance positron and electron beams, to explore methods to suppress the electron cloud, and to develop suitable advanced instrumentation required for these experimental studies (in particular a fast x-ray beam size monitor capable of single pass measurements of individual bunches). We report on progress with the CESR conversion activities, the status and schedule for the experimental program, and the first experimental results that have been obtained.
