Photoproduction of electron-positron pairs in bent single crystals

The process of photoproduction of electron-positron pairs in bent single crystals is considered in this paper. In particular, it is shown that the probability of the process for gamma-quanta with energies from 100 GeV on is significantly higher than the one in an amorphous medium. A possible scenario for the experimental validation of the process is discussed and the positive features of the photoproduction in bent crystals compared to straight ones are underlined from the point of view of possible applications.Comment: 13 pages, 6 figure

Crystal experiments on efficient beam extraction

Silicon crystal was channeling and extracting 70-GeV protons from the U-70 accelerator with efficiency of 85.3+-2.8% as measured for a beam of 10^12 protons directed towards crystals of 2 mm length in spills of 1-2 s duration. The experimental data follow very well the prediction of Monte Carlo simulations. This success is important to devise a more efficient use of the U-70 accelerator in Protvino and provides a crucial support for implementation of crystal-assisted collimation of gold ion beam in RHIC and slow extraction from AGS onto E952, now in preparation at Brookhaven Nat'l Lab. Future applications, spanning in the energy from sub-GeV (medical) to order of 1 GeV (scraping in the SNS, extraction from COSY) to order of 1 TeV and beyond (scraping in the Tevatron, LHC, VLHC), can benefit from these studies.Comment: 12pp. Presented at 19-th Intern. Conference on Atomic Collisions in Solids (ICACS-19: Paris, July 29 - August 3, 2001

Progress in crystal extraction and collimation

Recent IHEP Protvino experiments show efficiencies of crystal-assisted slow extraction and collimation of 85.3+-2.8%, at the intensities of the channeled beam on the order of 10^12 proton per spill of 2 s duration. The obtained experimental data well follows the theory predictions. We compare the measurements against theory and outline the theoretical potential for further improvement in the efficiency of the technique. This success is important for the efficient use of IHEP accelerator and for implementation of crystal-assisted collimation at RHIC and slow extraction from AGS onto E952, now in preparation. Future applications, spanning in the energy from order of 1 GeV (scraping in SNS, slow extraction from COSY and medical accelerators) to order of 1 TeV and beyond (scraping in Tevatron, LHC, VLHC), can benefit from these studies.Comment: 7pp. Presented at HEACC 2001 (Tsukuba, March 25-30

The Investigations Of Beam Extraction And Collimation At U-70 Proton Synchrotron Of IHEP By Using Short Silicon Crystals

The new results of using short (2-4mm) bent crystals for extraction and collimation of proton beam at IHEP 70 Gev proton synchrotron are reported. A broad range of energies from 6 to 65 GeV has been studied in the same crystal collimation set-up. The efficiency of extraction more than 85% and intensity more than 10E12 were obtained by using crystal with the length 2-mm and the angle 1 mrad. The new regime of extraction is applied now at the accelerator to deliver the beam for different experimental setups within the range of intensity 10E7-10E12ppp.Comment: Presented at EPAC 2002 (Paris, June 3-7), 3p