The Multi Optical Transition Radiation System
The determination and monitoring of the transverse phase space in ATF2 is crucial in order to meet their performances specifications. Since the beam sizes at the Interaction Point (IP) depend strongly on the aberrations in the Final Focus System (FFS), accurate measurement upstream of the FFS is required to tune the beam sizes at the IP. The beam sizes as well as the emittance are measured in several locations in the beam diagnostic section of the Extraction Line (EXT line) of ATF2. The vertical beam sizes in the diagnostic section are of the order of 10 {mu}m this means that the devices have to image spot sizes as small as 5 {mu}m, with 10% accuracy a 2 {mu}m resolution device is necessary. The ATF2 EXT line is a beam line with low power and low repetition rate that make usable devices using solid targets. In contrast to a ring machine, where an individual bunch can be measured many times as it passes around the ring, the beam size and the emittance measurement in the LC or in the beam lines have to be performed in a single pass. This requires that the wire scan device types (laser or solid) sample across successive bunches within a train, often with an over-estimation of the beam size due to beam position and intensity jitter, and can take up to half a minute to complete the measurement. Although some of these effects could be corrected, as the jitter effect could be subtracted by using the nearby BPMs signals, this can be avoided by using Optical Transition Radiation (OTR) Monitors. These monitors are based on the transition radiation effect, a light cone emitted when the charged particle crosses a metallic interface. This light is emitted in a specular fashion so it can be focused on to a CCD and produces an image of the beam. OTRs are able to take many fast measurements and therefore to measure the emittance with high statistics, giving a low error and a good understanding of the emittance jitter. In this article, simulations of the expected beam sizes and emittance, along with a technical description of the system, its hardware and software implementation are described. Additionally first measurement of the beam size and emittance of the Multi Optical Transition Radiation System located in the Extraction Line of ATF2 are presented.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 1038695
- Report Number(s):
- SLAC-REPRINT-2012-044; TRN: US1201956
- Journal Information:
- ICFA Beam Dynamics Newsletter, Vol. 54
- Country of Publication:
- United States
- Language:
- English
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ATF2 Summary and Status
Optical diffraction radiation from a beam off a circular target