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Title: Strategy for alignment of electron beam trajectory in LEReC cooling section

Abstract

We considered the steps required to align the electron beam trajectory through the LEReC cooling section. We devised a detailed procedure for the beam-based alignment of the cooling section solenoids. We showed that it is critical to have an individual control of each CS solenoid current. Finally, we modeled the alignment procedure and showed that with two BPM fitting the solenoid shift can be measured with 40 um accuracy and the solenoid inclination can be measured with 30 urad accuracy. These accuracies are well within the tolerances of the cooling section solenoid alignment.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1329782
Report Number(s):
BNL-112720-2016-IR
R&D Project: KBCH139; KB0202011; TRN: US1700405
DOE Contract Number:
SC00112704
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ELECTRON BEAMS; SOLENOIDS; ALIGNMENT; BROOKHAVEN RHIC; ELECTRON COOLING; ACCURACY; TRAJECTORIES; CONTROL; ELECTRIC CURRENTS; INCLINATION

Citation Formats

Seletskiy, S., Blaskiewicz, M., Fedotov, A., Kayran, D., Kewisch, J., Michnoff, R., and Pinayev, I. Strategy for alignment of electron beam trajectory in LEReC cooling section. United States: N. p., 2016. Web. doi:10.2172/1329782.
Seletskiy, S., Blaskiewicz, M., Fedotov, A., Kayran, D., Kewisch, J., Michnoff, R., & Pinayev, I. Strategy for alignment of electron beam trajectory in LEReC cooling section. United States. doi:10.2172/1329782.
Seletskiy, S., Blaskiewicz, M., Fedotov, A., Kayran, D., Kewisch, J., Michnoff, R., and Pinayev, I. 2016. "Strategy for alignment of electron beam trajectory in LEReC cooling section". United States. doi:10.2172/1329782. https://www.osti.gov/servlets/purl/1329782.
@article{osti_1329782,
title = {Strategy for alignment of electron beam trajectory in LEReC cooling section},
author = {Seletskiy, S. and Blaskiewicz, M. and Fedotov, A. and Kayran, D. and Kewisch, J. and Michnoff, R. and Pinayev, I.},
abstractNote = {We considered the steps required to align the electron beam trajectory through the LEReC cooling section. We devised a detailed procedure for the beam-based alignment of the cooling section solenoids. We showed that it is critical to have an individual control of each CS solenoid current. Finally, we modeled the alignment procedure and showed that with two BPM fitting the solenoid shift can be measured with 40 um accuracy and the solenoid inclination can be measured with 30 urad accuracy. These accuracies are well within the tolerances of the cooling section solenoid alignment.},
doi = {10.2172/1329782},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 9
}

Technical Report:

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  • The goal of this note is to set basic parameters for the magnetic shielding of LEReC CS with required design attenuation. We considered physical design of magnetic shielding of LEReC cooling section. The schematic of this design along with the list of its basic parameters is shown. We are planning to use 2 layers of 1 mm thick cylindrical mu-metal shields with μ=11000. The radius of the first layer sitting on top of vacuum chamber is 63.5 mm. The second layer radius is 150 mm. Such shielding guarantees adequate transverse angles of electron beam trajectory in the CS.
  • In the LEReC Cooling Section (CS) the RHIC ions are traveling together with and getting cooled by the LEReC electrons. The required cooling rate sets the limit of 150 urad on tolerable angles of the electrons in the CS. One of the components of overall electron angle is the angle of the e-beam trajectory with respect to the ion beam trajectory. We set the limit for electron trajectory angle to 100 urad. It is critical for preserving small trajectory angle to keep the transverse magnetic field inside the CS drifts within +/- 2.3 mG. The drifts in the CS mustmore » be shielded from the ambient magnetic fields of the RHIC tunnel, which can be as high as 0.5 G, to minimize the transverse field inside the CS vacuum chamber. In this paper we present the final design of the magnetic shielding of the LEReC CS and discuss the results of tests dedicated to studies of the shielding effectiveness.« less
  • For successful cooling the energies of RHIC ion beam and LEReC electron beam must be matched with 10 -4 accuracy. While the energy of ions will be known with required accuracy, e-beam energy can have as large initial offset as 5%. The final setting of e-beam energy will be performed by observing either Schottky spectrum or recombination signal from debunched ions co-traveling with the e-beam. Yet, to start observing such signals one has to set absolute energy of electron beam with accuracy better than 10 -2, preferably better than 5∙10 -3. The aim of this exercise is to determine whethermore » and how such accuracy can be reached by utilizing LEReC 180° bend as a spectrometer.« less
  • The Fermilab Electron Cooling Project requires low effective anglular spread of electrons in the cooling section. One of the main components of the effective electron angles is an angle of electron beam centroid with respect to antiproton beam. This angle is caused by the poor quality of magnetic field in the 20 m long cooling section solenoid and by the mismatch of the beam centroid to the entrance of the cooling section. This paper focuses on the beam-based procedure of the alignment of the cooling section field and beam centroid matching. The discussed procedure allows to suppress the beam centroidmore » angles below the critical value of 0.1 mrad.« less
  • Optical transiton radiation (OTR) produced from thin intercepting foils have been employed to image the spatial profile of the electron beam in several free electron laser experiments. It was found that the images from OTR were significantly sharper than the images produced from phosphor screens. Furthermore, OTR`s sensitivity of its angular distribution and polarization to energy and divergence of the electron beam was exploited to diagnose energy and emittance of the electron beam. OTR has been proven to be vital in electron beam alignment in FEL experiments. This report gives a summary of the basic theory of transition radiation andmore » techniques using transition radiation for electron beam imaging and emittance measurement. The possibility was explored for employing these techniques in the HGHG FEL and the visible FEL experiments in ATF (Accelerator Test Facility).« less