Minutes of the restricted Linac4 Diagnostics Working Group Meeting held on 13 July 2009

Present: C.Dutriat, B.Cheymol, E. Bravin, T.Hermanns, B.Mikulec.

Agenda:

1. Introduction (B.Mikulec)

2. Three monitors emittance measurement (T.Hermanns)

3. Multiple scattering simulations (B.Cheymol)

4. Discussion (all)

1. Introduction

B.Mikulec explained that the aim of this meeting was to identify possible technical solutions for an appropriate profile measurement to determine the emittance of the Linac4 160 MeV beam in the Linac4 dump line and before PSB injection.

2. Three monitors emittance measurement

T.Hermanns presented a short overview of the simulations that have been carried out by himself and B.Mikulec for an emittance measurement using 3 profile monitors in the Linac4 dump line (3MonitorsEmittanceMeasurement.pdf). The optics of the line have to be altered such that a beam waist of the beta function is produced at the central monitor position and that the beam ellipse turns by approximately 60 degrees between the 3 positions to obtain most efficient phase space sampling of the plane to be studied. The principal problem is that in order to reach small error values for the determination of the emittance, the beam size at the central monitor position gets very small (O(0.6 mm 1 sigma)). This implies that solutions should be found to be able to measure the beam size with an device with internal resolution around 10 um.

3. Multiple scattering simulations

The original idea was to use SEMgrid monitors with best obtainable resolution as profile detectors. The smallest technically feasible wire pitch is currently 300 um with 40 um thick tungsten wires, but C.Dutriat mentioned that this was challenging. Moreover with H- particles stripping will occur corresponding to the geometrical factor of the wire-to-spacing (15.4%). The particles that undergo stripping in the wire will moreover be scattered. B.Cheymol has simulated the effect of multiple scattering of 100k 160 MeV particles using FLUKA. 160-xy.bmp shows the distribution of the beam arriving at a 40 um thick tungsten foil (red) and the distribution 1 m later. The 1-dimensional deviation of the particle positions 1 m after the foil are also shown in this histogram (160-x.bmp). It can be seen that the average deviation 1 m after the foil is around 1 mm. This excludes an emittance measurement with the desired resolution with 3 SEMgrids in one shot.

-- BettinaMikulec - 14 Jul 2009

  • 160-x.bmp: Particle deviation of a 160 MeV beam 1 m after a 40 um thick tungsten foil.

  • 160-xy.bmp: 2D particle distributions of a 160 MeV beam before and 1 m after a 40 um thick tungsten foil.
Topic attachments
I Attachment History Action Size Date Who Comment
Bitmapbmp 160-x.bmp r1 manage 802.4 K 2009-07-14 - 18:05 BettinaMikulec Particle deviation of a 160 MeV beam after 40 um of tungsten foil.
Bitmapbmp 160-xy.bmp r1 manage 802.4 K 2009-07-14 - 18:07 BettinaMikulec 2D particle deviation of a 160 MeV beam before and 1 m after 40 um of tungsten foil.
PDFpdf 3MonitorsEmittanceMeasurement.pdf r1 manage 388.4 K 2009-07-14 - 18:02 BettinaMikulec Introduction into the 3 monitors emittance measurement in the Linac4 dump line.
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Topic revision: r1 - 2009-07-14 - BettinaMikulec
 
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