Beam Size Measurements

Beam Size Measurements

J. Turner, W. Colocho, Y. Feng, J. Krzywinski, H. Loos,

D. Ratner, J. Welch

2LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

Table of measurements

• 380eV 1/30/13: x-ray beam size with slits and profile monitors + gain length measurement of saturation point.

• 380eV 2/27/13: Electron beam size and match on Beam Finder Wires plus same as 1/30/13.

• 1200eV 2/18/13: Beam size vs. undulator length by orbit kick.

• 1200eV 3/5/13: e- size and match, x-ray size, gain length, x-ray size vs. blocks of undulators.

3LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

Measurements 1/30/13

• 380eV 1/30/13: • Fundamental below k-edge for N2, so

harmonics and fundamental both get cut roughly equally in the gas attenuator.– slit knife edge (FEE Slits 74.7m past end of

undulator, – x-ray profile monitors:

• YAGXRAY (45m past end of undulator) – Beam size and Gain Length measure of saturation point

• NFOV (Direct Imager 87m past end of undulator)

4LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

Initial 380eV Measurements 1/30/13

• Collimator Scan FEE Slit scans done with the other plane cut to a 1mm ribbon

• Rms x-ray size is C/sqrt(2)= ~700um

5LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

380eV Beam Size 1/30/13

• 380eV, CSR 0.5um C filter in. YAGXRAY, , there was no background subtraction of spontaneous, but zoom makes that baseline.

6LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

380eV Beam Size 1/30/13

• 380eV, CSR 0.5um C filter in. NFOV, there was no background subtraction of spontaneous. N2 attenuator set at 2.7torr (0.15% transmission)

7LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

380eV Beam Size 1/30/13

• 0.5um carbon filter. YAGXRAY Using kick method. Can't get a good gain length below saturation, but looks like saturation is reached around und #10

8LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

380eV Beam Size 1/30/13

• 0.5um carbon filter. YAGXRAY Using kick method. Power increase is linear beyond undulator 11.

9LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

Measurements 2/27/13

• 380eV 2/27/13:– Gain length measure of saturation point– Electron beam size and match on BFWs (beam

finder wires)– slit knife edge (FEE Slits 74.7m past end of

undulator, – x-ray profile monitors:

• YAGXRAY (45m past end of undulator) – Beam size and Gain Length measure of saturation point

• NFOV (Direct Imager 87m past end of undulator)

10LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

380eV Beam Size 2/27/13

• 0.5um C filter inserted (looking at mix of fundamental and third harmonic)Saturation around undulator 10.

11LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

2.7GeV (380eV) Beam Size 2/27/13

• 2.7GeV e- size (goes with 380eV x-ray data)

12LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

2.7GeV (380eV) Beam Size 2/27/13

• 2.7GeV e- size in undulator (goes with 380eV x-ray data)

13LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

2.7GeV (380eV) Beam Size 2/27/13

• 2.7GeV e- horizontal emittance and match in undulator (goes with 380eV)

14LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

2.7GeV (380eV) Beam Size 2/27/13

• 2.7GeV e- vertical emittance and match in undulator (goes with 380eV)

15LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

380eV Beam Size 2/27/13

• 380eV, Direct Imager intensity vs. Gas Attenuator transmission ratio with 1mj x-rays. Data at 0.2 transmission ratio. (~1.9torr)

16LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

380eV Beam Size 2/27/13

• 380eV, CSR 0.5um C filter in. NFOV. Poor Y fit, but X ok.

17LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

380eV Beam Size 2/27/13

• 380eV, CSR 0.5um C filter in. NFOV, move beam across screen. Same gas pressure as previous.

18LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

Measurements 2/18/13

• 1200eV 2/18/13: NFOV beam size vs. shortened undulator using corrector kick.

19LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

1200eV Beam Size 2/18/13

• 1200eV, 0.05% transmission at 4torr N2. NFOV. CSR filter was OUT during this scan. Mistake.

20LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

Measurements 3/05/13

• 1200eV 3/05/13: full gain length, electron beam size and (mis) match, beam size before and after mirrors. Cut off is 2200eV for SOMS, this eliminates all harmonics with the fundamental at 1200eV. X-ray beam size vs. blocks of undulators.

21LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

1200eV Beam Size 3/5/13

• 1200eV,

22LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

1200eV Electron Beam Size 3/5/13

• 1200eV, ~5.2GeV

23LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

1200eV Electron Beam Size 3/5/13

• 1200eV, ~5.2GeV

24LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

1200eV Electron Beam Size 3/5/13

• 1200eV, ~5.2GeV

• Horrible mismatch

25LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

1200eV Electron Beam Size 3/5/13

• 1200eV, ~5.2GeV

26LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

1200eV Beam Size 3/5/13

• 1200eV, CSR 0.5um C filter in. P3S1, 13% transmission N2 1.9torr

27LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

1200eV Beam Size 3/5/13

• 1200eV, CSR 0.5um C filter in. NFOV, 13% transmission N2 1.9torr. (X axis error of exactly factor of 2.)

674.2

28LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

1200eV Beam Size 3/5/13

• We took very rough beam size image data with u1:13 in followed by a strong xcor kick at u13. We also took data with u21:u33 in, all other segments out, and orbit corrected upstream of u21.Preliminary analysis of two such shots

• u1:13 yrms = 548 um, 12:48:52• u21:33 yrms = 738 um, 13:07:37• Note the strange relative size with the downstream section giving a

larger beam size than the upstream section. Evidently this technique did not work. The two sections were supposed to give the same divergence angle and only differ in the effective source location. We used a strict linear taper and had about 0.5 -0.7 mJ on the gas detector. Henrik worked on matching the beta function going into the undulator using correctors and BFW before we started the beam size measurements. There was a considerable mis-match that he did not have time to take out.

29LCLS Physics/Beam Size Measurements

Red Slate, 3/13/13

Summary

• About measurements: Important factors in obtaining a reasonable measurement are: elimination of CSR from first dump bend; background subtraction of the spontaneous x-rays; coping with cutoff in gas apertures; and capability of measuring and preventing saturation in either YAG profile monitors or cameras.

• 380eV data, though measurements were problematic due to cutoff in gas apertures, was was with a relatively matched electron beam and measurements are consistent with simulation. Simulation and measurement are just under 1mm rms which represents an upper bound on the measurements taken.

• x-ray beam size data with very large electron betatron mismatch (>2) differs by a factor of 2 from a matched simulation. Data taken on a day where the match was not measured showed a smaller beam.

• Future 1200eV study will be planned with a matched electron beam to verify the size.