Recent Progress in X-Ray Emittance Diagnostics at...

Recent Progress inX-ray Emittance Diagnostics

at SPring-8

S. Takano, M. Masaki, and H. Sumitomo *

JASRI/SPring-8, Hyogo, JapanSES, Hyogo, Japan *

Outline

Introduction

X-ray Pinhole Camera

X-ray Fresnel Diffractometry Monitor (XFD)

Conclusions

15 September 2015 IBIC 2015 Melbourne 1

IntroductionLight Source Facilities are Competing to

Achieve Lower Emittance and Emittance Coupling Ratio for Higher Brilliance.

Serious and Elaborate Efforts are being Paid forUpgrade Plans of Existing Rings or New Plans of Low Emittance Rings.

X-ray Synchrotron Radiation (SR) isKey Diagnostic Probe for Non-Destructive Beam Emittance Measurement.

Both Direct Imaging and Interferometric Techniquecan Resolve the Micrometer-order Transverse Beam Size.

Emittance is Obtained from the Measured Sizewith Other Knowledge (Betatron and Dispersion Functions, Energy Spread).


IntroductionTwo Alternative Targets of X-ray Emittance Diagnostics at Light Source Rings

Dipole Magnet Source and Insertion Device Source (Undulator)

It Seems from the View Point of Machine Operation thatEmittance Diagnostics of Dipole Source is Necessary and Sufficientfor Tuning the Beam of the Accelerator

Nonetheless,Diagnostics of Undulator Source Emittance Cannot be AvoidedBecause the Undulator is Just the Source of Light Delivered to Experimental Users

Two X-ray Instruments for Emittance Diagnostics Recently Implemented at SPring-8Dipole Source: X-ray pinhole cameraUndulator source: X-ray Fresnel Diffractometry monitor (XFD)


X-ray Pinhole Camera @ SPring-8


X-ray Window@ 6.24 m

Source:Dipole (29B2) Pinhole @ 11.43 m Scintillator @ 34.31 m

Layout



X-ray Window @ 6.2 mSource: Dipole (29B2)

B = 0.5 T Ec = 21.1 keV Aluminum 3mm thick

X-ray

Alminum 5052OFHC mask

1mm (H) X 5mm (V)

2 10134 10136 10138 10131 1014

1.2 10141.4 1014

0 50 100 150

Source

Filtered by X-ray Window

Flux

Den

sity

(pho

tons

/s/m

rad2

/0.1

%b.

w.)

Photon Energy (keV)



Pinhole Assembly @ 11.4 mY slit

Tungsten 3mm thick

X-ray

Aperture: 20 μm x 20μm

manual XZ stage

rotary stage

gonio stage

X slitTungsten 3mm thick



Scintillator & Camera Assembly@ 34.3mMirror

manual XZ stage

CCD Camera (Basler piA2400-17gm)GigE interface2448 x 2050 pixels3.45 μm x 3.45 μm pixel size

Lensobject-space

telecentricx2 magnificationW. D. = 111 mm

X-ray

ScintillatorCdWO4 (CWO)0.5mm thick



Resolution of Pinhole ( PSF calculation based on Wave Optics )

Pinhole Resolution (rms)

σdiff = 6.9 μm@ 42 kev

0

0.2

0.4

0.6

0.8

1

1.2

0 0.05 0.1 0.15

PSF

Inte

nsity

(a.u

.)

Y(mm) on the screen

Ep = 50 keV

0

5

10

15

20

30 35 40 45 50 55 60 65 70

Resolution (rms)

Res

olut

ion

(um

)

E (keV)0

5 1015

1 1016

1.5 1016

2 1016

2.5 1016

3 1016

0 50 100 150

Power absorbed by CWO (a.u.)

Abs

obed

Pow

er (e

V-1

)

E (keV)



Scintillator & Camera AssemblyResolution Calibration

Resolution (rms) ofScintillator & Camera Assembly

σCAM = 2.2 μm

sharpness of edge of W bar placed in front of scintillatormeasured

0

50

100

150

200

250

200 250 300 350 400

Inte

nsity

X (pxl)

0

10

20

30

40

260 280 300 320 340

dI/d

x

X(pxl)

σ = 2.2 um



Total Spatial Resolution σXPC (rms)

= 7.2 μm Pinhole σdiff = 6.9 μmScintillator & Camera σCAM = 2.2 μm

Scale of Camera Pixel to Beam Coordinate

measured by introducing vertical bump orbits

consistent withdesigned value 0.8625 μm/pixel

XPCσ = diffσ 2 + CAMσ 2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

830 840 850 860 870 880

y [m

m]

s [m]

29B2

-0.2

0

0.2

0.4

0.6

0.8

1000 1200 1400 1600 1800 2000

Y_b

ump

(mm

) Y (pxl)

0.848 um / pxl



Projected σx = 113.5 pixels

Projected σy = 21.3 pixels

Projected profiles(horizontal and vertical)consistent withGaussian profiles

Projected Beam Sizeσx = 96.0 μmσy = 16.6 μm

(resolution subtracted)

Example of data I = 100 mA, exposure time 1 ms

0

5

10

15

20

25

0 200 400 600 800 1000

Inte

nsity

(a.u

.)

X (pixel)

0 10 20 30 40 50 600100

200300

400500

Intensity (a.u.)

Y (pixel)



Control Room Display Live Beam Image View~ 15 fps

Parameters of Beam Profilebeam size σx and σybeam tilt angle θ

Continuously Loggedto SPring-8 Control Database

By Periodical Image Analysis(1s cycle time)

2D Gaussian Profile isFitted to Beam Image Data

εy = 7.5 pm.rad(coupling 0.3%)



Diagnostics for User Operation: Betatron Coupling induced by ID20

ID error fields excitebetatron couplingin user operation.

Betatron couplingis correctedby tuningskew Q parameters.

0

10

20

30

40

50

60

-0.5

0

0.5

1

1.5

2

2.5ID20 gap (mm) skew_Q_20_2

ID20

/ ga

p (m

m)

skew_Q

_20_2 / I (A)

12.5

13

13.5

14

14.5

1515

/7/9

0:0

0:00

15/7

/9 6

:00:

00

15/7

/9 1

2:00

:00

15/7

/9 1

8:00

:00

15/7

/10

0:00

:00

15/7

/10

6:00

:00

15/7

/10

12:0

0:00

15/7

/10

18:0

0:00

15/7

/11

0:00

:00

σy (μm)

σ y (

μm) gap closed skew Q correction

gap opened



Diagnostics for Machine Tuning: Betatron Coupling induced by ID10

Search forCorrecting skew Q parameters

Gap 6 mm Gap 50 mm (full-open)

* radiation induced-demagnetizationof ID10 suspected,and B field readjusted in March 2015

16

18

20

22

24

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 10 20 30 40 50 60

σ y (μ

m)

Tilt A

ngle (deg)

ID 10 Gap (mm)

14

15

16

17

18

19

20

-8 -7 -6 -5 -4 -3 -2 -1 0

gap 6 mmgap 8 mmgap 10 mm

Proj

eted

Ver

atic

al B

eam

Siz

e (u

m)

ΔI of skew Q magnets (A)



Preliminary Plan for SPring-8 Upgrade (SPring-8-II)

Source: Dipole MagnetLayout (distance from source)

Pinhole: 6.5m, Scintillator: 32m

PinholeMagnification ： x 3.9Size： 20 μm x 20 μm

Point Spread Function ( Wave Optics Calculation )

Pinhole Resolution (rms) better than 5 μmfeasible for 40 – 50 keV X-rays

Resolution of Present Scintillator Assemblyscales to 1.1 μm

0

0.2

0.4

0.6

0.8

1

1.2

0 0.05 0.1 0.15

PSF

Inte

nsity

(a.u

.)

Y(mm) on the screen

Ep = 40 keV

σ = 4.69 μm

X-ray Pinhole Camera @ SPring-8Summary

Live Beam Image View @ Control Room ~ 15 fpsParameters of Beam Profile Continuously Logged to SPring-8 Control DBIndispensable for Beam Tuning and User OperationResolution (rms) Better than 5 μm Feasible for Upgrade Plan of SPring-8


Specifications of the SPring-8 X-ray Pinhole Camera

Light Source Bending Magnent (29B2)

Pinhole Distance from Source (m) 11.4

Aperture Size (μm) 20 x 20

Scintillator Distance from Source (m) 34.3

Material CdWO4Camera Number of Pixels 2448 x 2050

Pixel Size (μm) 3.45 x 3.45

Magnification Factor x 4 ( Pinhole: x 2, Lens: x 2 )

Resolution (rms) (μm) 7.2 ( Pinhole: 6.9, Scintillator & Camera: 2.2 )


RLLRA+

≈ λ7

Diffraction patterns depending on a width A of the slitFraunhofer Diffractionnarrow slit (A2 Rλ )

X-ray Fresnel Diffractometry Monitor (XFD)Principle

Double-LobedFresnel Diffraction

The depth of a median dip correlates with a light source size.

optimum slit widthfor the deepest dip

M. Masaki et al., IBIC2014 TUCZB1 (2014).M. Masaki et al., Phys. Rev. ST Accel. Beams 18, 042802 (2015).

XFD @ SPring-8


ID05

- Nu=51- λu=76 mm

Monochromator

L = 26.8 m R = 65.4 m

X-ray cameraSlit

Setup for Initial Experiments

RLLRA+

≈ λ7optimum slit width Afor the deepest dip

- P43 Screen- lenses- CCD cameramin. exp. time: 1msresolution σres: 6.8 μm

XFD @ SPring-8


Initial Results M. Masaki et al., IBIC2014 TUCZB1 (2014).M. Masaki et al., Phys. Rev. ST Accel. Beams 18, 042802 (2015).

deep

erdi

p

(a) νx = 41.133, skew-Q on

(b) νx = 41.137, skew-Q off

(c) νx = 41.361, skew-Q off

(d) νx = 41.357, skew-Q off

a

b

c

d

X-ray energy 7.2 keV

slit width ΔY = 150 μm

0.5

0.6

0.7

0.8

0.9

1

-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2

exp. data

9.6 m

9.1 m

8.6 m

8.1 m

7.6 m

7.1 m

6.6 m

Norm

alize

d In

tens

ity

y (mm)

+ 0.5 μm

- 0.5 μm Best fit

Undulator source size smaller than 10 μmsuccessfully resolved

XFD @ SPring-8


Recent ProgressNew X-ray Imaging Setup

X-ray

Lens: x20

Imaging Resolution (rms) @ Source Point:2.2 μm

XFD


Summary

Diagnostic technique for light source ringsto measure small beam size at ID (undulator) source point

Able to resolve beam size smaller 5 μm

Requires onlyslit, monochromator, and imaging device (X-ray camera)

Has potential universal availability to ID beamlines of thediffraction limited storage rings (DLSRs)

Conclusions


SPring-8 X-ray Pinhole Camera

Resolution (rms) ~ 7 μm

Live Beam Image View @ Control Room ~ 15 fps

Beam Parameters Logged to Control DB by Periodical (1s cycle) Image Analysis

Indispensable for Beam Tuning and User Operation of SPring-8

X-ray Fresnel Diffraction (XFD) Monitor

Diagnostic Technique for Light Source Ringsto Measure Small Beam Size at ID (Undulator) Source Point

Requires OnlySlit, Monochromator, and Imaging Device (X-ray Camera)

Able to Resolve Beam Size smaller 5 μm

Acknowledgements


Many thanks to

colleagues of SPring-8/SACLA and SES

For their help in

vacuum, alignment, control and operation etc.


Thank you for your attention !

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