J-PARC, KEK & JAEA, Ibaraki-ken
KEK, Ibaraki
MINOTOS, Kunitachi, Tokyo Metropolitan
Morimoto Engineering, Iruma, Saitama
Kyoto University, Radioisotope Research Center, Kyoto-shi
UBE, Ichihara, Chiba
NIRS, Chiba-shi
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
We developed a secondary emission type beam profile monitor with multi ribbon target made of a carbon graphite foil. The carbon graphite foil is excellent in endurance against heat load, and its thickness as 1.6-3.0 micron and low z (=6) are advantage for reducing beam loss. Intense bunch up to 1013 particle per bunch has been measured. Furthermore, the ribbon emits larger amount of electrons than ordinal metal wires because of its larger surface. Therefore the monitor has higher sensitivity, and transverse beam tail has been observed clearly. The monitors were installed in injection transport and injection point of main ring in J-PARC, in order to measure beam profiles by single passing. Normal size target has 32ch ribbons with 2 or 3 mm in width and their length is 200 mm or more each. In this report, target fabrication, basic characteristics of the carbon graphite target, and results of beam measurement will be discussed.
MPQ, Garching, Munich
CERN, Geneva
The Linac4 at CERN will provide 160-MeV negative hydrogen beams of high intensity N =2x1014 ions/s. Before this beam can be injected into the CERN PS Booster or future Superconducting Proton Linac for further acceleration, some sequences of 500-ps-long micro-bunches must be removed from it, using a beam chopper. We developed a monitor to measure the time structure and spatial profile of this chopped beam, with resolutions 1 ns and 2mm. Its large active area 40mm x 40mm and dynamic range also allows investigations of beam halos. The ion beam first struck a carbon foil, and secondary electrons emerging from the foil were accelerated by a series of parallel grid electrodes. These electrons struck a phosphor screen, and the resulting image of the scintillation light was guided to a thermoelectrically cooled, charge-coupled device camera. The time resolution was attained by applying high-voltage pulses of sub-nanosecond rise and fall times to the grids. The monitor has been tested with 700-ps-long UV laser pulses, and a 3-MeV proton beam. Its response over a wide range of beam intensities between 5 and 4x108 electrons emitted from the foil per pulse was studied.
ORNL, Oak Ridge, Tennessee
Two electron scanners, one for each plane, have been installed in the SNS Ring to measure the profile of the high intensity proton beam. The SNS Ring accumulates 0.6 us long proton bunches of up to 1.6·1014 protons with a typical peak current of over 50 Amp during a 1 ms cycle. The measurement is non-destructive and can be done during production. Electron guns with dipoles, deflectors and quadropules scan pulsed electrons through the proton beam. The EM field of the protons change the electrons' trajectory and projection on a fluorescent screen. Cameras acquire the projected curve and analysis software determines the actual profile of the bunch. Each scan lasts only 20 nsecs, which is much shorter than the proton bunch. Therefore the longitudinal profile of the proton bunch can be reconstructed from a series of scans made with varying delays. This talk will describe the theory, hardware and software of the electron scanner as well as the results and progress made in improving the measurements.
PSI, Villigen
The challenges for beam current and transmission measurements at high intensity (2.2mA, 1.3MW) beam operation are presented. The monitors used for the current measurements are resonators tuned at the 2nd RF harmonic (101 MHz). While most all the monitors do not require specific attention, the monitor placed 8m behind a graphite target presents several challenges. This current monitor is placed in vacuum and the calculated heat load due to the heavy shower of energetic particles is about 230 Watts for 2 mA beam current. The resonator cooling has been improved (active cooling, improved radiation cooling and a modified mechanical structure) to minimize drifts due to the thermal expension. However, the gain drift during operation is of the order of 10%. These larger than expected drifts are actually induced by the non-homogeneity of the power deposition. To correct these dynamical drifts, some on-line corrective electronics using 2 tests signals 50 kHz off the RF frequency had to be developed. This provides an innovative mean to estimate on-line the resonator gain. Without these corrections this system would have been unusable for transmission measurements at high beam intensity.