Estimate of Undulator Magnet Damage Due to Beam Finder Wire Measurements

PDF Version Also Available for Download.

Description

Beam Finder Wire (BFW) devices will be installed at each break in the Undulator magnet line. These devices will scan small wires across the beam causing some electrons to lose energy through bremsstrahlung. The degraded electrons are subsequently detected downstream of a set of vertical dipole magnets after they pass through the vacuum chamber. This signal can then be used to accurately determine the beam position with respect to the BFW wire. The choice of the wire diameter, scan speed, and operating parameters, depends on the trade-off between the signal size and the radiation damage to the undulator magnets. In ... continued below

Creation Information

Welch, J. December 3, 2010.

Context

This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this report can be viewed below.

Who

People and organizations associated with either the creation of this report or its content.

Author

Publisher

Provided By

UNT Libraries Government Documents Department

Serving as both a federal and a state depository library, the UNT Libraries Government Documents Department maintains millions of items in a variety of formats. The department is a member of the FDLP Content Partnerships Program and an Affiliated Archive of the National Archives.

Contact Us

What

Descriptive information to help identify this report. Follow the links below to find similar items on the Digital Library.

Description

Beam Finder Wire (BFW) devices will be installed at each break in the Undulator magnet line. These devices will scan small wires across the beam causing some electrons to lose energy through bremsstrahlung. The degraded electrons are subsequently detected downstream of a set of vertical dipole magnets after they pass through the vacuum chamber. This signal can then be used to accurately determine the beam position with respect to the BFW wire. The choice of the wire diameter, scan speed, and operating parameters, depends on the trade-off between the signal size and the radiation damage to the undulator magnets. In this note I estimate the rate of undulator magnet damage that results from scanning as a function of, wire size, scan speed, and average beam current. A separate analysis of the signal size was carried out by Wu. The damage estimate is primarily based on two sources: the first, Fasso, is used to estimate the amount of radiation generated and then absorbed by the magnets; the second, Alderman et. al., is used to estimate the amount of damage the magnet undergoes as a result of the absorbed radiation. Fasso performed a detailed calculation of the radiation, including neutron fluence, that results from a the electron beam passing through a 100 micron diamond foil inserted just in front of the undulator line. Fasso discussed the signficance of various types of radiation and stated that photoneutrons probably play a major role. The estimate in this paper assumes the neutron fluence is the only significant cause of radiation-induced demagnetization. The specific results I use from Fasso's paper are reproduced here in Figure 1, which shows the radial distribution of the integrated neutron fluence per day in the undulator magnets, and Figure 2, which shows the absorbed radiation dose all along the undulator line. In the longitudinal dimension, Fasso's calculation, (see Figure 2), shows that the radiation dose is widely distributed all along the undulator line, but is highest around 70 m from the front of the undulator line where the foil is. At the 70 m point, for the purpose of calculating the demagnetization, I chose a conservative estimate for the effective neutron flux of 1.0 x 10{sup 13} n/cm{sup 2}/day. As can be seen in Figure 1, this choice is representative of the flux nearest the beam where it is the highest. A less conservative estimate, but perhaps more accurate, estimate of the effective flux, would be the average flux in the magnet block, which is roughly one half as much.

Language

Item Type

Identifier

Unique identifying numbers for this report in the Digital Library or other systems.

  • Report No.: SLAC-TN-10-067
  • Grant Number: AC02-76SF00515
  • DOI: 10.2172/993717 | External Link
  • Office of Scientific & Technical Information Report Number: 993717
  • Archival Resource Key: ark:/67531/metadc1014580

Collections

This report is part of the following collection of related materials.

Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

What responsibilities do I have when using this report?

When

Dates and time periods associated with this report.

Creation Date

  • December 3, 2010

Added to The UNT Digital Library

  • Oct. 14, 2017, 8:36 a.m.

Description Last Updated

  • Nov. 2, 2017, 8:11 p.m.

Usage Statistics

When was this report last used?

Yesterday: 0
Past 30 days: 0
Total Uses: 1

Interact With This Report

Here are some suggestions for what to do next.

Start Reading

PDF Version Also Available for Download.

Citations, Rights, Re-Use

Welch, J. Estimate of Undulator Magnet Damage Due to Beam Finder Wire Measurements, report, December 3, 2010; [California]. (digital.library.unt.edu/ark:/67531/metadc1014580/: accessed December 14, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.