LBNL, Berkeley, California
We present electron-cloud build-up simulations for the FNAL Main Injector at the location of the RFA electron detector. By comparing our simulated results against measurements for various bunch intensities and beam fill patterns, we determine the likely value of the peak secondary emission yield. We then extrapolate our results to higher intensities, within the range contemplated by the proposed MI upgrade program. We predict a substantial increase of the electron cloud density relative to its present value. We consider two values of the RF frequency, namely 53 and 212 MHz, and compare the electron cloud density for these two frequencies at fixed total beam intensity. We contrast the MI results against those from a similar simulation for the PS2, the first storage ring in the proposed future upgrade of the LHC injector complex. Time permitting, we will briefly comment on effects from the electron cloud on the beam dynamics.
BNL, Upton, Long Island, New York
NSCL, East Lansing, Michigan
CERN, Geneva
Isochronous cyclotrons, rings for precise nuclear mass spectrometry, and some isochronous-optics light sources with extremely short bunches are operated or proposed to be operated in the isochronous or almost isochronous regime. Also, many hadron synchrotrons run in the isochronous regime for a short period of time each acceleration cycle during transition crossing. The longitudinal motion is “frozen” in the isochronous regime that leads to accumulation of the integral of the longitudinal space charge force. In low-gamma hadron machines, this can cause a fast growth of the beam energy spread even at modest beam intensities. In this paper, I discuss specifics of space charge in the isochronous regime and present experimental results obtained in the Small Isochronous Ring, developed at Michigan State University specifically for studies of space charge in the isochronous regime.
KEK, Ibaraki
University of Tennessee, Knoxville, Tennessee
ORNL, Oak Ridge, Tennessee
At the 39th ICFA HB2004 workshop and the EPAC-2006 conference, we reported the lifetime and properties of the HBC (Hybrid type Boron-mixed Carbon) foils, a newly developed material, measured by the use of a 3.2 MeV Ne+ ion beam, which deposits significant energy in the foil due to the heavy ion. The content reported showed superior durability against high temperature damage due to foil deformation, thickness reduction and pinhole production at 1700 ± 100K compared with the cluster foils made by the CADAD method. This time, we measured the lifetime of the HBC-foils and the high quality nanocrystalline diamond foils including commercially available foils at 1800 ± 100K which induces the high temperature damage. The measurements were performed by using the KEK-650 keV high intensity H- and DC beam, which generates the same energy deposition as the RCS of J-PARC. In this workshop, we report the results obtained.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
A 3GeV Rapid-Cycling Synchrotron (RCS) in Japan Proton Accelerator Research Complex (J-PARC) has been commissioned since September 2007. The most important issue in the beam study is to reduce unnecessary beam loss and to keep the beam line clean for the sake of maintenance and upgrade of the machines. From experience of the former accelerators, the average beam loss should be kept at an order of 1 watt per meter for hands-on maintenance. Since it is very difficult to control the beam loss at such a low level, the only measure we can take is to localize any of the losses in a restricted area, where deliberate modules should be provided for quick coupling and remote handling in order to mitigate the personal doses. Accordingly, we have designed the beam collimation system for the purpose of the beam loss localization. We report the performance of the beam collimation system of RCS through the first commissioning results and the residual doses around RCS components.
Fermilab, Batavia, Illinois
The High Intensity Neutrino Source (HINS) program at Fermilab will demonstrate new technologies suitable for the low-energy front-end of a high intensity H- linac based on independently phased superconducting resonators (driven by a single power source). Eighteen β. = 0.21 superconducting single spoke resonators, operating at 325 MHz with an nominal accelerating field of 10 MV/m, comprise the first stage of the linac cold section. For two prototype resonators, we report on the construction phases and the comparison of low gradient RF measurements with calculations. After Buffered Chemical Polishing and High Pressure Rinse at Argonne, one resonator has undergone high gradient RF testing at 2.0° 4.5°Kelvin in the Vertical Test Stand (VTS) at Fermilab. We present measurements from the VTS tests, including BCS resistance and the quality factor as a function of accelerating field. In order to help understand multipacting and field emission, RTD temperature sensors were mounted on the exterior walls of the cavity, and x-ray sensing diodes were mounted near the cavity in the liquid helium bath. The resonator reached an accelerating field of 13.4 MV/m.