non-intercepting beam size monitor using optical diffraction radiation

$: Non-intercepting Beam Size Monitor using Optical Diffraction Radiation$
Non-intercepting Beam Size Non-intercepting Beam Size Monitor using Optical Diffraction Monitor using Optical Diffraction

RadiationRadiation

Tanaji SenTanaji SenFNAL FNAL

forfor A. Lumpkin, R. Moore, V. Scarpine, T. Sen, A. Lumpkin, R. Moore, V. Scarpine, T. Sen,

R. Thurman-Keup, M. WendtR. Thurman-Keup, M. Wendt

US LARP Collaboration Meeting, April 24, 2008US LARP Collaboration Meeting, April 24, 2008

T. Sen: LARP CM10T. Sen: LARP CM10 ODR MonitorODR Monitor 22

OutlineOutline

Background on ODRBackground on ODR

Critical parametersCritical parameters

Far-field spectrumFar-field spectrum

Near-field spectrumNear-field spectrum

ODR Monitor in the TevatronODR Monitor in the Tevatron

ODR in the LHCODR in the LHC

ProposalProposal


Progress since October 2007Progress since October 2007

Detailed report on far-field ODR (LARP doc 711)Detailed report on far-field ODR (LARP doc 711)

Near field spatial distribution (A. Lumpkin)Near field spatial distribution (A. Lumpkin)

Synchrotron radiation background (R.Thurman-Synchrotron radiation background (R.Thurman-Keup)Keup)

Collaboration on ongoing experiments at JLAB, Collaboration on ongoing experiments at JLAB, DESY (A. Lumpkin)DESY (A. Lumpkin)

Mechanical design startedMechanical design started

Space allocated in TevatronSpace allocated in Tevatron

Decision on installation schedule (Spring 2009)Decision on installation schedule (Spring 2009)


What is ODR?What is ODR?Generated when a charged particle passes near a Generated when a charged particle passes near a conducting surface. conducting surface. Non-invasive technique to measure beam properties.Non-invasive technique to measure beam properties.Can be generated in a straight section unlike Can be generated in a straight section unlike synchrotron radiation.synchrotron radiation.Backward ODR is imaged at the same longitudinal Backward ODR is imaged at the same longitudinal location as the targetlocation as the targetCan be observed in the far-field (Fraunhofer zone)Can be observed in the far-field (Fraunhofer zone)Can be observed in the near-field (Fresnel zone)Can be observed in the near-field (Fresnel zone)Potential applications toPotential applications to

Leptons: ILC, XFEL, ERLs, Muon colliderLeptons: ILC, XFEL, ERLs, Muon collider Protons: Tevatron, LHCProtons: Tevatron, LHC


Brief History of ODRBrief History of ODREarly theory developed in the late 1950sEarly theory developed in the late 1950sObservation of coherent DR from electron bunch in 1995Observation of coherent DR from electron bunch in 1995Observation of incoherent DR in the far-field from Observation of incoherent DR in the far-field from electron bunches in 2003 (KEK)electron bunches in 2003 (KEK)Beam size and position measurement in 2004 (KEK)Beam size and position measurement in 2004 (KEK)Interference between transition and diffraction radiation Interference between transition and diffraction radiation in 2005 (BNL)in 2005 (BNL)Beam size and position measurement with the near field Beam size and position measurement with the near field from electron bunches in 2007 (APS: Lumpkin)from electron bunches in 2007 (APS: Lumpkin)Measurements at KEK, APS, BNL, DESY, CEBAF, …Measurements at KEK, APS, BNL, DESY, CEBAF, …

14 papers in Phys. Rev. Lett and PRSTAB since 1995, 6 14 papers in Phys. Rev. Lett and PRSTAB since 1995, 6 in 2007-2008in 2007-2008


Diffraction Radiation - LayoutDiffraction Radiation - Layout

BDR

Camera or PMT

Filter

Polarizer

TargetProton beam

b Impact parameterBeam

2Φ

Φ

Far field imaging at KEKPhys. Rev Letters90, 104801 (2003)93, 244802 (2004)

Near field image at APSPRSTAB:10,022802(2007)

Target

Effective source sizeat target = (γλ)/2π


ODR critical parametersODR critical parametersImpact parameter bImpact parameter b

Wavelength Wavelength λλ

Energy Energy γγ

ODR intensity is ODR intensity is significant when significant when

b ~ b ~ γ λγ λ/(2/(2ππ))

Intensity falls whenIntensity falls when

b >> b >> γ λγ λ/(2/(2ππ))

Beam divergence << Beam divergence << 1/ 1/ γγ in hadron beams in hadron beams

Transverse fields from a particle Ex ~ (x / r┴) K1(2π r┴/γλ) -> (x/ r┴

(3/2)) exp[-2 π r┴/(γλ)]


Round hole: Far-field angular spectrumRound hole: Far-field angular spectrum

The angular spectrum peaks at The angular spectrum peaks at ωω = = ωωccAt fixed frequency, the ODR spectrum has peaks at At fixed frequency, the ODR spectrum has peaks at θθ ~1.6/ ~1.6/γγThe minimum and maximum values and the locations of the The minimum and maximum values and the locations of the extrema are sensitive to the beam size and beam position.extrema are sensitive to the beam size and beam position. Ratio of minima to maxima can be used to determine beam size.Ratio of minima to maxima can be used to determine beam size.

Relative frequency

AngleAngle

σ2 > σ1

σ1

LARP doc 711


Round hole: far-field spectrumRound hole: far-field spectrum

Angular spectra (log scale) at 1 and 3 microns for Tevatron and LHCAngular spectra (log scale) at 1 and 3 microns for Tevatron and LHCAt 3 microns, LHC spectrum is 4 orders of magnitude larger than in At 3 microns, LHC spectrum is 4 orders of magnitude larger than in the Tevatronthe TevatronThe relative difference grows larger as the wavelength is decreased.The relative difference grows larger as the wavelength is decreased.


Rectangular slit: far-field spectrumRectangular slit: far-field spectrum

Angular spectra at 1 and 3 microns for Tevatron Angular spectra at 1 and 3 microns for Tevatron and LHC from a rectangular slit.and LHC from a rectangular slit.Similar features as with the round holeSimilar features as with the round hole


Sensitivity to beam sizeSensitivity to beam size

Ratio of minimum to maximum increases quadratically with beam Ratio of minimum to maximum increases quadratically with beam sizesizeSensitivity increases with frequencySensitivity increases with frequencyIntensity changes at the few% level will detect beam size changes Intensity changes at the few% level will detect beam size changes of fractions of of fractions of σσ

b=8σ

Smaller relative beam size or larger separation

LARP doc 711P. Karataev et al PRL (2004)

Measurement at KEK


Round hole: Photon yieldsRound hole: Photon yields

Tevatron: Tevatron: σσ=0.4mm at =0.4mm at C0C066σσ clearance clearance =>=>λλcc=14=14μμm (u=1) m (u=1) => => λλ = 2.8 = 2.8 μμm (u=5) m (u=5)

--------------------------------------------------------------LHC: 18m from IP with LHC: 18m from IP with ββ*=0.25m (after IR *=0.25m (after IR upgrade), upgrade), σσ=0.8mm =0.8mm 77σσ clearance clearance =>=>λλcc=4.7=4.7μμm (u=1) m (u=1) => => λλ = 0.94 = 0.94μμm (u=5) m (u=5)

Photon yield/bunch/turn in a 10% bandwidth

Tevatron: Integrating over 36bunches

and 1 second amplifies this by 1.7x106

LARP doc 711

Nph ~ exp[-1.8ω/ωc] for ω > ωc


Tevatron: Beam size from near fieldTevatron: Beam size from near field Tevatron examples (γ=1044, λ=1.6 µm ) for beam-size monitor Left: σx=400 µm and varying d from 2-8 mm, Right: σx=400 µm ± 20%, σy=400 µm, d = 6 σy.

Perpendicular polarization Courtesy of C.-Y. Yao, ANL


LHC: LHC: Beam size from near fieldBeam size from near field LHC examples for beam-size monitor for σx=800 µm and varying d from 4.8-8 mm (L), and with σx=800 µm ± 20%, σy=800 µm, d = 6 σy, λ=1.0 µm, and γ=7500 (R).

Perpendicular polarization Courtesy of C.-Y. Yao, ANL


Beam position from near-fieldBeam position from near-field

OTR and ODR image centroid track BPM OTR and ODR image centroid track BPM – – see A. Lumpkin’s talk (CM10)see A. Lumpkin’s talk (CM10)


Place for ODR in the TevatronPlace for ODR in the TevatronProposed C0 Section for Installation

Space exists at C0 within a drift space for an ODR monitor For protons, the nearest upstream dipoles are 11m away and they are weak The synchrotron light monitor is close by and can be used for cross-calibration.

Courtesy: K. Duel


Synchrotron radiation backgroundSynchrotron radiation background24

2016

128

40

mm

121086420-2-4-6-8-10-12mm

400x103

300

200

100

0Photons / s / 0.1%

bw / m

m2

3000 nm

2422

2018

1614

1210

86

42

mm

600x103

500

400

300

200

100

0

Photons / s / 0.1%

bw / m

m 2

3000 nm

Vertical polarization (3 microns)

Vertical polarization with mask

Courtesy: R. Thurman-Keup


SR background at 1 micronSR background at 1 micron24

2016

128

40

121086420-2-4-6-8-10-12mm

40x103

30

20

10

0

Photons / s / 0.1%bw

/ mm

2

1000 nm

2422

2018

1614

1210

86

42

0m

m

121086420-2-4-6-8-10-12mm

40x103

30

20

10

0

Photons / s / 0.1%

bw / m

m 2

1000 nm

Vertical polarization (1 micron)

Vertical polarization with mask

Courtesy: R. Thurman-Keup


ODR Schematic/ OTR monitorODR Schematic/ OTR monitor

Courtesy: V. Scarpine

OTR monitor in the Tevatron at E0


Mechanical drawing of 10 way crossMechanical drawing of 10 way cross

Courtesy: K. Duel


ODR Monitor in the LHCODR Monitor in the LHC

ODR monitor would be ODR monitor would be stationed between the stationed between the detector and 1detector and 1stst quadrupole – quadrupole – left and right side of IRleft and right side of IRFrom From ββ(-L), (-L), ββ(L) we can (L) we can measure measure ββ*,*,αα**Not affected by errors Not affected by errors elsewhere in the machine.elsewhere in the machine.Non-invasive measurement Non-invasive measurement of beam size and relative of beam size and relative beam position during a store.beam position during a store.Regular arc dipoles are Regular arc dipoles are ~260m from IP~260m from IP

ODR monitor


Pros/Cons of ODR in the LHCPros/Cons of ODR in the LHCPros. Pros.

Non-invasive measurement of the beam size at the IPNon-invasive measurement of the beam size at the IPMeasurement itself will not be influenced by optics errorsMeasurement itself will not be influenced by optics errorsThis can be used to diagnose gradient errors in the IR.This can be used to diagnose gradient errors in the IR.Relative beam position measurements can be compared Relative beam position measurements can be compared against BPM measurements in the IR.against BPM measurements in the IR.Bunch by bunch measurement may be possibleBunch by bunch measurement may be possible

ConsConsSlower than synchrotron light monitor. Signal will have to Slower than synchrotron light monitor. Signal will have to be integrated over several turns.be integrated over several turns.Errors associated with the measurement are not well Errors associated with the measurement are not well known. Measurements in the Tevatron will determine the known. Measurements in the Tevatron will determine the limits of resolution.limits of resolution.The ODR monitor would be installed between the TAS The ODR monitor would be installed between the TAS and the 1st quad. Impact on the machine-detector and the 1st quad. Impact on the machine-detector interface needs to be better understood. interface needs to be better understood.


ODR Monitor proposalODR Monitor proposalGoal: To demonstrate the feasibility of ODR to Goal: To demonstrate the feasibility of ODR to measure beam size and position in a collider.measure beam size and position in a collider.StepsSteps

(1) Design the ODR monitor for the Tevatron(1) Design the ODR monitor for the Tevatron (2) Install monitor at C0 in Spring 2009 (next (2) Install monitor at C0 in Spring 2009 (next

shutdown)shutdown) (3) Set up monitor for proton beam (3) Set up monitor for proton beam

measurements during shot set-up and beam measurements during shot set-up and beam studiesstudies

(4) Proceed to use the monitor during luminosity (4) Proceed to use the monitor during luminosity storesstores

(5) Design an ODR monitor for LHC parameters(5) Design an ODR monitor for LHC parameters


Features of ODR ProposalFeatures of ODR Proposal

First test of ODR in a collider. The Tevatron First test of ODR in a collider. The Tevatron offers a unique opportunity to further develop offers a unique opportunity to further develop ODR – but the window is short.ODR – but the window is short.Well defined start and end of taskWell defined start and end of task

- Design and build now, install in Spring ‘09- Design and build now, install in Spring ‘09 - Ends with the Tevatron run in ‘10- Ends with the Tevatron run in ‘10

ODR/OTR experts involvedODR/OTR experts involved Budget requestBudget request

FY09: Labor: 1 FTE (to support 4-5 people),FY09: Labor: 1 FTE (to support 4-5 people), M&S: $50KM&S: $50K

FY10: Request will depend on progress in FY09, FY10: Request will depend on progress in FY09, will be mostly for labor.will be mostly for labor.


PeoplePeople

A. Lumpkin, V. Scarpine, T. Sen, G. A. Lumpkin, V. Scarpine, T. Sen, G. Tassotto, R. Thurman-Keup, M. WendtTassotto, R. Thurman-Keup, M. Wendt

Tevatron dept. Tevatron dept.

Mechanical Engineering deptMechanical Engineering dept

Look forward to a collaboration with CERNLook forward to a collaboration with CERN

Experts from other US labs welcomeExperts from other US labs welcome


SummarySummaryODR has the potential to become a standard ODR has the potential to become a standard diagnostic tooldiagnostic toolProposed ODR monitor in the Tevatron will be Proposed ODR monitor in the Tevatron will be the first test with a circulating beam.the first test with a circulating beam.LARP support is essential for test to proceed.LARP support is essential for test to proceed.Success in the Tevatron will advance the state Success in the Tevatron will advance the state of the art. of the art. ODR signals in the LHC will be orders of ODR signals in the LHC will be orders of magnitude stronger than in the Tevatron at the magnitude stronger than in the Tevatron at the same wavelength, or use lower wavelengths same wavelength, or use lower wavelengths (~1/3(~1/3rdrd) in the LHC) in the LHCImaging near the IP will provide an independent Imaging near the IP will provide an independent way to optimize luminosityway to optimize luminosity


BackupsBackups


Measuring β*, α*Measuring β*, α*

Beam size, hence β, is measured at +L, -LBeam size, hence β, is measured at +L, -L

α* = [β(-L) – β(+L)]/4Lα* = [β(-L) – β(+L)]/4L

β* = ( [< β>2 + 4(1+ α*2)L2]1/2 - < β>)/2)β* = ( [< β>2 + 4(1+ α*2)L2]1/2 - < β>)/2)

< β> = [β(-L) + β(+L)]/2< β> = [β(-L) + β(+L)]/2

This measurement of β*, α* is independent This measurement of β*, α* is independent of optics errorsof optics errors


Signal Intensity Levels EstimatedSignal Intensity Levels EstimatedEstimated signal has strong dependence on Estimated signal has strong dependence on ααb=2b=2ππb/b/γλγλ..

Courtesy of Yao, Lumpkin

Log 1

0 α

2K

12

Units of 2πb/γλ

FLASH, 0.8 µm

Tev-2,1.6 µm

Tev-1,1.0 µm

LHC1,1.6 µm

LHC-2,1.0 µm b values


SR background- wide viewsSR background- wide views-2

5-2

0-1

5-1

0-5

05

1015

2025

mm

757065605550454035302520151050-5-10-15-20-25mm

12x106

10

8

6

4

2

0

Photons / s / 0.1%bw

/ mm

2

3000 nm

-25

-20

-15

-10

-50

510

1520

25m

m

757065605550454035302520151050-5-10-15-20-25mm

500x103

400

300

200

100

0

Photons / s / 0.1%

bw / m

m2

3000 nm

3 microns

Total Intensity

Vertical polarization

non-intercepting beam size monitor using optical diffraction radiation

Documents