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Lee, Y.

Paper Title Page
MOPD64 Visual Inspection of a Copper Collimator Irradiated by 590 MeV Protons at PSI 245
 
  • A. Strinning, S.R.A. Adam, P. Baumann, V. Gandel, D.C. Kiselev, Y. Lee
    PSI, Villigen
 
 

In March 2010 one of the most exposed collimators of the 590 MeV proton beam line at PSI, was visu-ally inspected after 20 years of operation without failure. It is made out of OFHC copper and cooled by water tubes. At currents of 2.2 mA, the temperature inside the collimator is ~ 350 C. From the total beam charge of 120 Ah, ~15 % are absorbed. The main motivation for the inspection was to investigate the present condition of the collimator after the long exposure in a high intensity proton beam. According to MARS15 the inner parts have seen 35 DPA. For the inspection, the collimator was removed remotely from the beam line by a shielded exchange flask and transferred to the hot cell. In order to enter the collimator opening and examine the inner structure without any contact or damage, a special tool was built, using the principle of a periscope. By moving and rotation the tool with the power manipulator, sharp pictures of the inner surface were taken with a high resolution reflex camera, operated remotely. Because of the high radiation (> 50 Sv/h in 0.2 m) camera and electronics were shielded. After the inspection, the collimator was built in to the beam line again.

 
WEO2A04 Current and Transmission Measurement Challenges for high Intensity Beams 443
 
  • P.-A. Duperrex, V. Gandel, D.C. Kiselev, Y. Lee, U. Müller
    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.

 

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THO2A03 New Design of a Collimator System at the PSI Proton Accelerator 567
 
  • Y. Lee, P. Baumann, V. Gandel, D.C. Kiselev, D. Reggiani, M. Seidel, A. Strinning, S. Teichmann
    PSI, Villigen
 
 

PSI is gradually upgrading the 590 MeV proton beam intensity from the present 2.2 mA towards 3 mA, which poses a significant challenge to the reliable operation of the accelerator facility. Of particular concern is the collimator system which is exposed to the dispersed beam from a muon production target. It shapes an optimal beam profile for low-loss beam transport to the neutron spallation source SINQ. The collimator system absorbs slightly more than 10 % of the proton beam power and the maximum temperature of the collimator system exceeds 350 C at 2.2 mA, which is close to the failure point. In this paper, we present a new collimator system design which could withstand the proton beam intensity of 3 mA, while fulfilling the intended functionalities. Advanced multi-physics simulation technology is used for the geometric and material optimizations, to achieve the lowest possible actual to yield stress ratio at 3 mA. A sensitivity study is performed on the correlation between the beam misalignments and the reliability of the key accelerator components in the proton downstream region. Also reported are the possible proton irradiation effects on the mechanical failure criteria.

 

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