Beam-Prof rofil ile M e Monitor I or Issues ues a at A0PI: The - - PowerPoint PPT Presentation

Beam-Prof rofil ile M e Monitor I

• r Issues

ues a at A0PI: The C Case f for r Reduced E Emit mittances

Alex Lumpkin for the A0 team Presented at A0 MTG June 19, 2009 Batavia, Illinois

Emittan tance M ce Measurem urement ent I Issues es

• Measurements
• f

beam transverse emittances and longitudinal emittance are needed for the incoming and

• utgoing values in the EEX experiments.
• Identify, characterize, and apply needed corrections.
• Corrections to the observed projected image profile sizes

are warranted.

– Camera resolution term of 1.8 to 2.0 pixels can be in play. – YAG:Ce powder screens have a limiting spatial resolution term.

• Consider corrections at X5 slit images.
• Consider corrections at XS3 energy spread measurement.
• Consider corrections at X24 slit images.
• The previously reported EEX table results from Feb. 6

and Feb. 11, 2009 should be revised.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 2

Iden entif tify C Correc ections tions t to Consid ider er

• Camera resolution
• Slit finite size
• YAG:Ce powder screen spatial resolution
• Beta star term in spectrometers
• Macropulse blurring effects on energy spread , beam

size, and beam divergence in OTR images.

• OTR polarization effects.
• Camera calibration factor.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 3

Uncorrected Solenoid Current (A)

180 190 200 210 220 230 240 250

Emittance x,y (mm mrad)

2 4 6 8 10 2/6/09 vs X4-Xemit-raw 2/6/09 vs X5-Xemit raw 2/6/09 vs X4-Yemit-raw 2/6/09 vs X5-Yemit raw

Observed d vs Actu ctual Sl Slit t Image Si e Size

• Uncorrelated terms are treated as a quadrature sum to

actual image size as in Lyons’ book a.

• - actual (Act) image size, camera resolution (cam),

YAG screen effects (YAG), finite slit width (slit). ( In addition there can be macropulse effects and OTR polarization effects.)

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 4

Obs2 =Act2 + YAG2 +cam2 + slit2

• Eq. 1

Solving for the actual beam size we have, Act = [Obs2 - YAG2- cam2- slit2]½

• Eq. 2

aLouis Lyons: Statistics for Nuclear and Particle

Physicists (1986)

Observed d vs Actu ctual X XS3 S3 Image Si e Size

• Uncorrelated terms are treated as a quadrature sum to

actual image size as in Lyons’ book a.

• - actual (Act) beam size for energy spread, camera

resolution (cam), YAG screen effects (YAG), and nondispersed beam size βxεx/γ.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 5

Obs2 =Act2 + YAG2 +cam2 + βxεx/γ

• Eq. 3

Solving for the actual beam size we have, Act = [Obs2 - YAG2- cam2- βxεx/γ]½ = ηxσE

• Eq. 4

aLouis Lyons: Statistics for Nuclear and Particle Physicists (1986)

YAG:Ce Ce P Powd wder er Sc Scinti tillator S Scr cree eens

• The screens have nominally a 5-µm grain size and are

coated at 50-µm thickness on various metal substrates.

• Usually the A0 substrates are Al or SS and 1 mm thick.
• In the A0 geometry the scintillator is on the front

surface and oriented at 45 deg to the beam direction.

• The response time is about 80 ns FWHM.
• There have been reports of saturation of the mechanism

for incident electron beam areal charge densities of 10 fC/µm2.

• This effect can cause a charge dependence of the
• bserved image size in addition to the low charge,

screen resolution limit.

• Screens provided by Klaus Floettmann at DESY.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 6

Recent ent C Chrono nolog logy

• Tim K. mentions a Chromox screen used in XS3 in Feb.

09 meeting. Initial screen res. concerns raised by AHL.

• Detailed description of emittance determinations given

by Yin-E on Feb. 11 EEX data.

• This talk showed the beam sizes used in pixels at X4,

X5, XS3, X24 for the transverse and longitudinal emittances.

• Hypothesis on limiting resolution of scintillator screen

invoked based on Chromox data.

• Question on minimum spatial size term from emittance

at XS3 also raised.

• Opened XS3 station and found a darkened YAG powder

screen and darkened port window.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 7

Chara racteri cterize T ze Terms

• YAG:Ce scintillator screen has a limiting resolution

term that must be addressed.

• YAG powder screen used in XS3.
• YAG powder screens used with slit images at X5 and

X24.

• Actions:

1) At XS3 install new YAG screen with an OTR thin foil

• ver the top half of the screen. Allows direct

comparison of two image sources. March 25. 2) Review data of Feb. 6 and 11, 2009 and find systematic effect of YAG screen vs. OTR. Feb.-March 3) Install X22 two-screen actuator at X5. May 22 4) Evaluate camera resolution and slit term at X4, X24.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 8

XS3 3 Sp Spectr trometer I Images (0 (04-23-09) 9)

• Micropulse charge of 250 pC used; 20 bunches for OTR
• image. Deduced YAG:Ce res. term of σ=180 µm.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 9

YAG:Ce, σ=5.0 pixels=235 µm OTR, σ=3.2 pixels=150 µm

X24 I Ima mages ( (04-23-09) 09)

• Micropulse charge of 250 pC used. Deduced YAG res.

term of σ=176 um for this areal charge density.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 10 10

YAG:Ce, σy=7.0 pixels OTR: σy=4.3 pixels

Ini Initial XS XS3 and nd X2 X24 OTR-YAG YAG r res esults ts (4 (4-23-09 Da Data ta)

11 11

Table I: Comparison of YAG:Ce and OTR beam images at 250 pC per bunch. Location Screen

• No. Bunches

Fit sigma (pix) Size (µm) XS3 YAG 1 5.0 235 XS3 OTR 10 3.15 150 XS3 OTR 20 3.24 152 X24 YAG-2 1 7.0 224 X24 OTR 20 4.3 138

*The simple quadrature rule gives a YAG screen resolution of 180 um at XS3

and 176 um at X24 for this charge and beam sizes. (The simple quadrature rule at X5 implied 140-180 um for slit image charges before May 22, 2009.)

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009

XS3 I 3 Images es Exhibit t So Some Ch Char arge De Depen ende dence (4 e (4-27-09) 9)

12 12

Table II: Comparison of YAG:Ce and OTR beam images at XS3.

Location Screen Charge (pC)

• No. Bunches

Fit sigma (pix) Size (µm) XS3 YAG 150 1 4.82 227 YAG 200 1 5.04 237 YAG 250 1 5.26 247 XS3 OTR 150 10 3.20 150 OTR 200 10 3.46 163 OTR 250 10 3.75 176 *The beam sizes are 7-image Gaussian fit averages. The implied XS3 YAG screen resolution terms are 170,172, and 173 µm for the increasing charges, respectively.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009

Em Emittan ttance u e using X X3 and X4(O 4(OTR) R)-Sl Slit I t Images es (0 (02-11-09 Da 9 Data ta)

mrad mm 5 . 3 m 0.39 mm/pixel 0.0267 pixels 2.33 mm 78 . 28 m 39 Hslits)

• 4

x ( ) 3 x ( mrad mm 3 . 3 m 0.39 mm/pixel 0.0275 pixels 2.33 mm 73 . 28 m 39 Vslits)

• 4

x ( ) 3 x ( = ⋅ ⋅ ⋅ = = = ⋅ ⋅ ⋅ = = . / . /

y y y n x x x n

σ γσ ε σ γσ ε

13 13

Em Emittan ttance u e using X X3 and X5 5 (Y (YAG)-slit it Images (2 (2-11-09) 9)

mrad mm 1 . 5 m 0.80 ixel 0.0271mm/p pixels 6.91 mm 78 . 28 m 80 Hslits)

• 5

x ( ) 3 x ( mrad mm 7 . 4 m 0.80 mm/pixel 0.0268 pixels 6.82 mm 73 . 28 m 80 Vslits)

• 5

x ( ) 3 x ( = ⋅ ⋅ ⋅ = = = ⋅ ⋅ ⋅ = = . / . /

y y y n x x x n

σ γσ ε σ γσ ε

14 14 A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009

Energy gy s spre read a d at stra raigh ght lin line

σE=5.5 pixels; Disp.=0.324 m; δp/p= (5.5 pixels *0.0593mm/pixel) /Disp.=0.1%

εn

z=γσz δp/p=28*0.75 mm*0.1%

=21 mm mrad

15 15 A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009

Tra ransverse e emit mittances a after E r EX

16 16

mrad mm . 6 m 0.565 mm/pixel 0.032 pixels 5.4 mm 70 . 28 m 565 Hslits)

• 4

x2 ( ) 3 x2 ( mrad mm 21 0.565m mm/pixel 0.032 pixels 4.5 mm 92 . 2 28 m 565 Vslits)

• 4

x2 ( ) 3 x2 ( = ⋅ ⋅ ⋅ = = = ⋅ ⋅ ⋅ = = . / . /

y y y n x x x n

σ γσ ε σ γσ ε

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009

Dom Dominos Step Steps (outg (outgoing)

17 17

• For the outgoing transverse emittance we apply the est. 130 µm YAG:Ce

screen resolution to the X24 slit image data. This is 4.0 pixels with the reported 32 um per pixel calibration in x and y.

• The observed X24 slit image sizes were 5.4 and 4.5 pixels which are

corrected to 3.6 and 2.06 pixels for y and x divergences, respectively.

• The outgoing emittances are then εx=9.8 mm mrad and εy =4 mm mrad,

revised downward from 21 and 6 initially.

• The outgoing longitudinal emittance was reported as 7.1 mm mrad. The

spectrometer beam image size was 11.2 ch X 85 µm per pixel, however the βyεy term has not been determined or subtracted yet. This is an OTR screen. The bunch length was reported as 0.85 ps.

• The emittance term in XS4 needs determination as indicated by the revised

EEX table. The bunch length probably needs a redo with new optics.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009

Summa mary Feb

• Feb. 11,

11, 2009 2009: E EEX m X meas easurements

18 18

mrad mm 6 mrad mm 5 ~ 4 mrad mm 7 mrad mm 21 mrad mm 21 mrad mm 5 ~ 3 → = → = → =

y n z n x n

ε ε ε

Before EEX After EEX

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009

Initia itial C l Correcti tions to 2-11 11-09 D 09 Data

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 19 19

• Corrections applied : camera res. 1.8, 2.0 pixels, X5

YAG screen 160 µm. Cam res ~1.3 pixels and YAG 180 µm at XS3. Newer YAG, est. 130 µm res. at X24 only.

Camera Date Pixels OTR x,y Pixels YAG x,y Pixel Corr. x,y X4 2-11-09 2.33, 2.33 1.38,1.48 X5 6.82, 6.91 2.84, 3.05 XS3 2-11-09 5.5 4.38 X24 2-11-09 4.5, 5.4 1.94 , 3.6

Summa mary –propos

• sed

ed r revisions

• ns

Feb

• Feb. 11,

11, 2009 2009: E EEX m X meas easurements

20 20

mrad mm 3.9 mrad mm 2.3 mrad mm 7 mrad mm 17 mrad mm 3 . 9 mrad mm 1 . 2 → = → < = →< =

y n z n x n

ε ε ε

Before EEX After EEX

*Need to determine the beam size without dispersion in XS3.

Need to determine the minimum beam size without dispersion in XS4. Subsequent tests in 2009 have incoming longitudinal emittance of ~10 mm mrad with 250 pC. Also used γ=29.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009

Sole lenoid s d scan ( (02-06-09) 09)

• Proposed revisions to beam size values reduce X4 and

X5 emittance data. Cam res. 1.8, 2.0 pix; YAG=160 µm.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 21 21 Uncorrected Solenoid Current (A)

180 190 200 210 220 230 240 250

Emittance x,y (mm mrad)

2 4 6 8 10 2/6/09 vs X4-Xemit-raw 2/6/09 vs X5-Xemit raw 2/6/09 vs X4-Yemit-raw 2/6/09 vs X5-Yemit raw

Corrected Solenoid Current (A)

180 190 200 210 220 230 240 250

Emittance x,y (mm mrad)

2 4 6 8 10 2/6/09 vs X4-Xemit corr 2/6/09 vs X4-Yemit-corr 2/6/09 vs X5-Xemit-corr 2/6/09 vs X5-Yemit-corr

Asses essments nts a at X4,X5, 5, X X6

• In the May 19 solenoid current scan on emittance we took slit

images at X4 (OTR), X5 (YAG), and X6 (OTR) for the first time.

• One notes the small X4 slit image sizes of 2-3 pixels.
• We verify the lens F#’’s are all 1.4 and 2.0 in X3-X6.
• By comparing the slit images from X4 to X6, we deduce a camera

resolution plus slit size contribution of about 2 pixels. This is significant in quadrature at X4.

• Randy independently checked the camera resolution terms on the
• ptical bench.
• We deduce a YAG screen resolution term of about 180 um from a

X4-X5 image size comparison after subtracting a cam. res. term.

• We now note that the slit image separations were 1.03,0.95, and

0.82 mm for X4, X5, and X6, respectively. Residual fields????

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 22 22

Sole lenoid S d Scan Data (5 Data (5-19-09)

• Corrections for camera resolution+slit term (2 pix) and

YAG screen resolution term (180 µm) are applied below.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 23 23

Uncorrected Solenoid Current (A)

190 200 210 220 230 240 250 260

X- Emittance (mm mrad)

2 4 6 8 10 12 5/19/09 X4-x emit raw 5/19/09 X5-xemit raw 5/19/09 X6 x-emit raw

Uncorrected Solenoid Current (A)

190 200 210 220 230 240 250 260

Y Emittance (mm mrad)

2 4 6 8 10 12 5/19/09 X4-y emitt raw 5/19/09 X5 y-emit raw 5/19/09 X6-y-emit raw

2D Graph 3 Solenoid Current (A)

190 200 210 220 230 240 250 260

X Emittance Corrected (mm mrad)

2 4 6 8 10 12 5/19/09 X4-x emit corr 5/19/09 X5-xemit-corr 5/19/09 X6-xemit-corr

2D Graph 4 Solenoid Current (A)

190 200 210 220 230 240 250 260

Y Emittance Corrected (mm mrad)

2 4 6 8 10 12 5/19/09 X4 Yemit-corr 5/19/09 X5 Yemit-corr 5/19/09 X6-Yemit-corr

X5 X4 X6 X5 X4 X6

Direct C ect Compar arison o

• n of YAG-OTR

TR S Slit I t Image ages at at X5 X5 (M (May 27, 27, 2009 2009)

• Table I: Comparison of YAG:Ce and OTR beam slit images at 250

pC per bunch at X5, drift of 0.8 m. Location Screen

• No. Bunches

Fit sigma (pix) Size (µm) X5 YAG 5 7.2 ~194 X5 OTR 100 4.9 ~132 * The deduced screen resolution term is 140 µm, but there could be a macropulse effect and OTR polarization effect to unravel. The X22 YAG and OTR screens were installed at X5 on 5/22/09. Average of fits to 5 images used. This is a “newer” YAG screen from EEX line.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 24 24

Sug Suggested Fur Furthe ther Step Steps

• Need specific slit image tests at X5 with YAG and OTR. Is the

X5-X4 deduced resolution term of 140 µm at low charge right?

• Need specific slit image tests at X24 with YAG and OTR. Is the

X5-X4 deduced resolution term of 140 µm at low charge right?

• We need the real minimum non-dispersed beam size in XS3.

Amber has some data to process.

• I propose using the U1 cross in the user line to check the OTR

beam size without dispersion. Any focusing effects of the dipole for XS3 would be needed from Philippe or others.

• We need the real minimum non-dispersed beam size in XS4.
• We need to check bunch lengths also after EEX at X24 and

wakefield effects in the dipole vac. chambers.

• An additional OTR polarization effect on image size is being

checked at X5.

25 25 A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009

SUMM MMARY

• The uncorrelated correction terms for screen

resolution and camera resolution cannot be ignored for 250 pC slit image size and spectrometer data.

• The reduced actual beam sizes lead to reduced

emittance values (3,3,10) and new exchange studies.

• Macropulse effects need to be minimized so YAG-OTR

comparison is accurate.

• Sort out the slit-image low areal charge density effect.
• OTR polarization effect is being explored: seems real.
• PITZ data of 2-3 years ago have some effects , but

recent data is reported to be from 25 µm YAG on 250 µm Si substrate oriented normal to beam.

• Upgraded diagnostics options at A0 available for use.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 26 26

Upgr grade ded D d Dia iagn gnostics f for r EEX

• We have added capabilities all through the machine.

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 27 27

1) We now have both OTR and YAG at X5 for divergence measurements. 2) We have demonstrated use of X6-OTR for the slit images. Need zero fields in quads. 3) We have had simultaneous UV laser and X9 OTR signals to the streak camera. 4) We have both OTR and YAG screen options at XS3. We see smaller images with OTR. (Still need the beta-x-emittance-x product term defined and subtracted in quadrature). 5) We have a better understanding of the YAG screen limiting resolution term and camera res. term at X4, X5,X6, XS3, and X24. Still need Beta* terms. 6) We do have the mirror optics on the streak camera, and our BW term is reduced.. but not fully yet. This is for X24 bunch length measurements. We are proceeding with the new parabolic mirror installation at X24.The interferometer is still operational. Hopefully, we will have a prescription for the solenoid coils and bucking coil currents for best emittance.

Possib ible A le Assem emblies ies

A.H. Lumpkin A A0PI 0PI M Mtg. June e 19, 19, 2009 2009 28 28

• Switchable assemblies to compare options. Still tweaking.

Impedance Screen YAG:Ce, plus Al onSi Mirror OTR, Normal to beam, plus Al on Si mirror Impedance Screen OTR foil, 1µm plus1µm foil at 45 deg

Option 1 Option 2

OTR 100 µm Al plus Al on Si Mirror

Screen Mirror

Beam

Light