Date of Award
Summer 2005
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical & Aerospace Engineering
Program/Concentration
Mechanical Engineering
Committee Director
J- K. Huang
Committee Member
S. K. Nanda
Committee Member
G. Hou
Call Number for Print
Special Collections; LD4331.E56 D44 2005
Abstract
Upcoming experiments at Hall A at Jefferson lab require 1 % absolute accuracy of the electron beam polarization measurement at 0.85 Ge V energy. The Compton polarimeter at Hall A is capable of measuring beam polarization with 3 - 4 % accuracies at this beam energy. Hence it was proposed to upgrade the present Compton by doubling the laser frequency [2]. The present Compton polarimeter operates with a 1064 nm, continuous wave laser at 200 mW. This power is enhanced to 1.5 kW using a 0.85 m long Fabry-Perot Cavity. Changing to 532 nm laser with the same power would result in a 3 kW enhancement with similar cavity parameters. A change in· the photon source requires considerable changes in the photon system of the Compton polarimeter. This comprises of polarizing optics, mode matching optics, steering optics, feedback control and the cavity.
The present cavity is a monolithic cavity with fixed mirrors. The two mirrors forming the cavity are aligned by design due to high tolerances applied on the cavity enclosure. The mirrors have a short life time, about 2 years as their performance degrades due to close proximity with the electron beam. The cavity, which is placed along the beam line, needs to be removed completely to replace the mirrors. This is to be followed by a tedious task of bench-top alignment During this process, the mirrors are susceptible to miss-alignment due to operator error or manufacturing flaws that exist in the mirror itself. After this the cavity has to be replaced in the beam line and the laser, re-aligned to the cavity. This procedure requires a few days with an overhead of man hours and stalled experimental beam time. If the alignment is disturbed during this procedure, the entire task needs to be repeated. Hence, a cavity with adjustable mirrors, in-situ mirror replacement and in-situ alignment method is worth investigating.
For testing the feedback control system and optics, a resonating cavity is needed in addition to laser characterization. As a first pass towards achieving this goal, a prototype cavity is designed to test the adjustable mirrors within a working photon system.
The proposed cavity length of 0.85 m is accompanied with difficulties in alignment and locking. A con-focal cavity on the other hand, is a cavity with length equal to the radius of curvature of the mirrors and is hence easier to lock. The cavity mirrors have a radius of curvature of 0.5 m and hence a length of 0.5 mis chosen for the prototype.
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DOI
10.25777/qbc1-qs84
Recommended Citation
Deepa, Deepa.
"Design and Fabrication of A Prototype Fabry-Perot Cavity for the Compton Polarimeter Upgrade at Jefferson Lab"
(2005). Master of Science (MS), Thesis, Mechanical & Aerospace Engineering, Old Dominion University, DOI: 10.25777/qbc1-qs84
https://digitalcommons.odu.edu/mae_etds/465
Included in
Engineering Physics Commons, Mechanical Engineering Commons, Plasma and Beam Physics Commons