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Title: Bunch coalescing in the main ring to form intense proton and antiproton bunches without RF counterphasing

Abstract

Both the proton and antiproton bunches which will collide in the Tevatron have longitudinal emittance greater than can be accelerated by the main ring from 8 GeV without large loss and emittance growth. We have previously described the technique of combining several smaller bunches at the Tevatron injection energy with little increase in the total emittance and negligible loss. This technique requires adiabatic debunching of several adjacent 53 MHz bunches by smooth reduction of the RF voltage from approx. 1 MV to approx. 100 V. The very low voltage is extremely difficult to attain with a high-Q system designed for megavolt accelerating potential. The counterphasing technique of voltage reduction which we have used in main ring experiments and proposed for the TeV I project is to divide the accelerating cavities into two closely matched groups and to smoothly shift the relative phase of the drive to the two groups by 180 degrees. When the net voltage has been reduced by this means to the lowest practical level, about 10 kV, the final voltage reduction may be performed by turning off the high-Q system and using a low-Q cavity. The voltage induced on the undriven gaps of the high-Q system ismore » low enough not to be a major problem because the total intensity is low. However, the effects are not negligible, and dynamic beam loading compensation is required. This memo proposes that the process described above be simplified somewhat by replacing the counterphasing voltage reduction with a zero-voltage spreading of the bunches for several milliseconds followed by a few hundred microseconds of rotation to minimum energy spread in buckets produced at high voltage.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Fermi National Accelerator Lab., Batavia, IL (USA)
OSTI Identifier:
6557129
Report Number(s):
FNAL-TM-1280
ON: DE85001364
DOE Contract Number:  
AC02-76CH03000
Resource Type:
Technical Report
Resource Relation:
Other Information: Portions are illegible in microfiche products
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; TEVATRON; BEAM BUNCHING; ANTIPROTON BEAMS; BEAM EMITTANCE; PROTON BEAMS; THEORETICAL DATA; ACCELERATORS; ANTINUCLEON BEAMS; ANTIPARTICLE BEAMS; BEAM DYNAMICS; BEAMS; CYCLIC ACCELERATORS; DATA; INFORMATION; NUCLEON BEAMS; NUMERICAL DATA; PARTICLE BEAMS; SYNCHROTRONS; 430200* - Particle Accelerators- Beam Dynamics, Field Calculations, & Ion Optics

Citation Formats

Griffin, J E, MacLachlan, J A, Nicholls, G N, and Qian, Z B. Bunch coalescing in the main ring to form intense proton and antiproton bunches without RF counterphasing. United States: N. p., 1984. Web. doi:10.2172/6557129.
Griffin, J E, MacLachlan, J A, Nicholls, G N, & Qian, Z B. Bunch coalescing in the main ring to form intense proton and antiproton bunches without RF counterphasing. United States. https://doi.org/10.2172/6557129
Griffin, J E, MacLachlan, J A, Nicholls, G N, and Qian, Z B. Thu . "Bunch coalescing in the main ring to form intense proton and antiproton bunches without RF counterphasing". United States. https://doi.org/10.2172/6557129. https://www.osti.gov/servlets/purl/6557129.
@article{osti_6557129,
title = {Bunch coalescing in the main ring to form intense proton and antiproton bunches without RF counterphasing},
author = {Griffin, J E and MacLachlan, J A and Nicholls, G N and Qian, Z B},
abstractNote = {Both the proton and antiproton bunches which will collide in the Tevatron have longitudinal emittance greater than can be accelerated by the main ring from 8 GeV without large loss and emittance growth. We have previously described the technique of combining several smaller bunches at the Tevatron injection energy with little increase in the total emittance and negligible loss. This technique requires adiabatic debunching of several adjacent 53 MHz bunches by smooth reduction of the RF voltage from approx. 1 MV to approx. 100 V. The very low voltage is extremely difficult to attain with a high-Q system designed for megavolt accelerating potential. The counterphasing technique of voltage reduction which we have used in main ring experiments and proposed for the TeV I project is to divide the accelerating cavities into two closely matched groups and to smoothly shift the relative phase of the drive to the two groups by 180 degrees. When the net voltage has been reduced by this means to the lowest practical level, about 10 kV, the final voltage reduction may be performed by turning off the high-Q system and using a low-Q cavity. The voltage induced on the undriven gaps of the high-Q system is low enough not to be a major problem because the total intensity is low. However, the effects are not negligible, and dynamic beam loading compensation is required. This memo proposes that the process described above be simplified somewhat by replacing the counterphasing voltage reduction with a zero-voltage spreading of the bunches for several milliseconds followed by a few hundred microseconds of rotation to minimum energy spread in buckets produced at high voltage.},
doi = {10.2172/6557129},
url = {https://www.osti.gov/biblio/6557129}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1984},
month = {8}
}