ODR Diagnostics ODR Diagnostics for Hadron for Hadron CollidersColliders

Tanaji SenTanaji SenFNAL/APCFNAL/APC

Acknowledgements: A. Lumpkin, V. Scarpine, R. Thurman-Keup, M. Wendt

T. Sen; 10/18/2007 ODR for Hadron colliders

Diffraction RadiationRadiation emitted when a charged particle passes Radiation emitted when a charged particle passes in the in the vicinityvicinity of a conducting target. of a conducting target. Two cones (angle ~ 2/Two cones (angle ~ 2/γγ ) of radiation in the forward ) of radiation in the forward and backward directionand backward direction Key parameters: the impact parameter, beam Key parameters: the impact parameter, beam energy and wavelength of radiationenergy and wavelength of radiation

Similar (and different) to transition radiation where a Similar (and different) to transition radiation where a particle passes particle passes throughthrough the conducting target. the conducting target.

Main advantage: Non-invasive Main advantage: Non-invasive

Initial theory developed: ~ 1960sInitial theory developed: ~ 1960s First measurements reported: ~1995First measurements reported: ~1995

T. Sen; 10/18/2007 ODR for Hadron colliders

Possible Beam Possible Beam DiagnosticsDiagnosticsDiffraction Radiation ObservablesDiffraction Radiation Observables

Near field (at or near target) intensityNear field (at or near target) intensity PolarizationPolarization Frequency spectrumFrequency spectrum Far field angular distributionFar field angular distribution Interference between radiation from 2 sourcesInterference between radiation from 2 sources

These can be combined to potentially measureThese can be combined to potentially measure Beam sizeBeam size Beam positionBeam position Beam divergenceBeam divergence EnergyEnergy

Recent measurements at KEK, APS, FLASHRecent measurements at KEK, APS, FLASH Interest at other labs: CEBAF, BNLInterest at other labs: CEBAF, BNL

T. Sen; 10/18/2007 ODR for Hadron colliders

Diffraction Radiation - Diffraction Radiation - LayoutLayout

BDR

CCD 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

T. Sen; 10/18/2007 ODR for Hadron colliders

KEK results (slit target)KEK results (slit target)

Imax

T. Sen; 10/18/2007 ODR for Hadron colliders

KEK SummaryKEK Summary Electron beam energy=1.28 GeV, Electron beam energy=1.28 GeV, γγ=2505=2505 Bunch intensity = 1.2 x 10Bunch intensity = 1.2 x 101010

Beam size = 10 Beam size = 10 μμm, m, divergence= 3.8x10divergence= 3.8x10-3-3(1/(1/γγ)) Impact parameter ~ 5Impact parameter ~ 5σσyy Detected wavelengthDetected wavelength λλ = 0.56 = 0.56 μμmm Synchrotron radiation background Synchrotron radiation background

from dipole 8m upstream; used a maskfrom dipole 8m upstream; used a mask ODR intensity = 58% of OTR intensityODR intensity = 58% of OTR intensity Measured sensitivity to beam size ~ Measured sensitivity to beam size ~ 14 14

μμmm

T. Sen; 10/18/2007 ODR for Hadron colliders

APS APS

10σ

10 σ10 σ

16σ

T. Sen; 10/18/2007 ODR for Hadron colliders

APS Summary APS Summary Electron beam energy = 7GeV, Electron beam energy = 7GeV, γγ= 13,699= 13,699 Bunch intensity ~ 1.9x10Bunch intensity ~ 1.9x101010 (3 nC). Tevatron (3 nC). Tevatron

proton intensity ~ 43 nCproton intensity ~ 43 nC Beam sizes: Beam sizes: σσxx = 1375 = 1375 μμm, m, σσyy = 200 = 200 μμmm Typical impact parameter ~ 6 Typical impact parameter ~ 6 σσyy Wavelength Wavelength λλ ~ 0.83 ~ 0.83 μμmm ODR signals observed up to 16 ODR signals observed up to 16 σσyy ODR signals (@ 6 ODR signals (@ 6 σσyy) about 10% of OTR signal) about 10% of OTR signal Sensitive to horizontal offsets of 50-100 Sensitive to horizontal offsets of 50-100 μμmm Sensitive to beam size changes of 20-50 Sensitive to beam size changes of 20-50 μμmm

T. Sen; 10/18/2007 ODR for Hadron colliders

Hadron colliders: key Hadron colliders: key parametersparameters

TevatronTevatron RHICRHIC LHCLHCEnergy [GeV]Energy [GeV]Bunch intensityBunch intensityTarget clearance Target clearance [[σσ]] Beam size [Beam size [μμm]m]Wavelength[Wavelength[μμm]m]Beam Beam div/opening div/opening angleangleFar-field distance Far-field distance [m] [m]

9809802.7x102.7x101111

12 812 839939914.414.4

2.9x102.9x10-3-3

2.52.5

250250 2x102x101111

12 12 88101210121431431.2x101.2x10-5-5

1.61.6

700070001.1x101.1x1011

11

12 12 888078074.14.1

5.7x105.7x10--

33

36.136.1

T. Sen; 10/18/2007 ODR for Hadron colliders

Different target shapesDifferent target shapes Straight edge – APS (near-field), Straight edge – APS (near-field),

KEK (far-field)KEK (far-field)

Rectangular slit – KEK (far-field)Rectangular slit – KEK (far-field)

Round hole Round hole

T. Sen; 10/18/2007 ODR for Hadron colliders

Round holeRound hole Intensity Intensity

distribution from a distribution from a single particle (PSF) single particle (PSF) depends only on depends only on these parametersthese parameters

g, u, g, u, γθγθ Otherwise it does Otherwise it does

not depend on the not depend on the inner radius ainner radius a<<

Number of photons Number of photons emitted (far-field)emitted (far-field)

Inner radius a<. Outer radius a>

Key parameters Critical frequency ωc = γc/a< Radii ratio g = a>/a< Scaled frequency u = ω / ωcΔΔNNγγ = ( = (ββ//ππ))ααff u u22 F(g, u) F(g, u)

ΔΔω/ω

T. Sen; 10/18/2007 ODR for Hadron colliders

Far-field spectral distributions Far-field spectral distributions (round hole)(round hole)

For g =1.1,Number of photons emitted /bunch/turn ΔNγ ~ 1.6 x 106

T. Sen; 10/18/2007 ODR for Hadron colliders

Rectangular SlitRectangular Slit Angular spectral Angular spectral

distribution from a distribution from a bunch depends onbunch depends on

Slit widthSlit width RMS sizeRMS size Bunch transverse Bunch transverse

offsetoffset Observation Observation

angles angles θθx, x, θθyy

tx= γθx, ty = γθy

T. Sen; 10/18/2007 ODR for Hadron colliders

Far-field spectral Far-field spectral distributions (slit)distributions (slit)

Wavelength dependence

LHC

TEV

Beam parameter dependence

T. Sen; 10/18/2007 ODR for Hadron colliders

Far-field spectral distributionFar-field spectral distribution(straight edge)(straight edge)

Characteristic Characteristic λλcc = 2 = 2ππb/b/γγ At b = 4.8mm, At b = 4.8mm, λλcc = 28 = 28 μμm m

(TEV)(TEV) Spectrum at Spectrum at ωω > 0.2 > 0.2 ωωcc

Photon yield/bunch/turnPhoton yield/bunch/turn

At At ωω = 2 = 2 ωωcc or or λλ=14 =14 μμm,m, ΔΔN = 4.4 x 10N = 4.4 x 1066

photons/bunch/turnphotons/bunch/turn

]53.1exp[48.0cd

dW

bNddWN

T. Sen; 10/18/2007 ODR for Hadron colliders

InterferometryInterferometry

Beam

Interference from Interference from multiple aperturesmultiple apertures

Forward DR from 1st target interferes with backward DR from 2nd targetInterference pattern is sensitive to beam divergenceDistance between targets should be comparable to far field distance. Rules this out for the LHCMay be difficult for very small beam divergences

FDR

BDR

T. Sen; 10/18/2007 ODR for Hadron colliders

ODR location in the ODR location in the TevatronTevatron

Drift space around Drift space around C0 is 11mC0 is 11m

4 dipoles upstream, 4 dipoles upstream, 2 dipoles 2 dipoles downstream in the downstream in the proton directionproton direction

Beta functions are Beta functions are in the range 60-in the range 60-85m85m

Preferable to image Preferable to image pbars closer to the pbars closer to the 4 dipoles ?4 dipoles ?

11 m

protons

Optics around C0

T. Sen; 10/18/2007 ODR for Hadron colliders

Empty space in C0Empty space in C0

T. Sen; 10/18/2007 ODR for Hadron colliders

LHC InsertionLHC Insertion

Regular arc dipoles Regular arc dipoles are ~260m from IPare ~260m from IP

Weak separation Weak separation dipoles (~1.5T) at dipoles (~1.5T) at 60m from IP60m from IP

ODR monitor ODR monitor would be stationed would be stationed between the between the detector and 1detector and 1stst quadrupole – left quadrupole – left and right side of IRand right side of IR

260m260m

Measuring Measuring ββ*, *, αα** Beam size, hence Beam size, hence ββ, is , is

measured at +L, -Lmeasured at +L, -L αα* = [* = [ββ(-L) – (-L) – ββ(+L)]/4L(+L)]/4L ββ* = ( [<* = ( [< β β>>22 + 4(1+ + 4(1+

αα**22)L)L22]]1/21/2 - < - < β β>)/2)>)/2) << β β> = [> = [ββ(-L) + (-L) + ββ(+L)]/2(+L)]/2 This measurement of This measurement of ββ*, *, αα* *

is independent of optics is independent of optics errorserrors

T. Sen; 10/18/2007 ODR for Hadron colliders

IP

-L L

T. Sen; 10/18/2007 ODR for Hadron colliders

Layout in the LHCLayout in the LHCIP5: Horizontal IP5: Horizontal

Crossing AngleCrossing AngleIP1 : Vertical Crossing Angle

b

b

BDR Cone

BDR Cone

Target at 45 to beam direction

Beam 1

Beam 2

T. Sen; 10/18/2007 ODR for Hadron colliders

Design decisionsDesign decisions Location of the target; both beams should not Location of the target; both beams should not

be present simultaneously, far enough from be present simultaneously, far enough from dipoles, …dipoles, …

Determine the synchrotron radiation Determine the synchrotron radiation background at the targetbackground at the target

Determine the optimal shape and material of Determine the optimal shape and material of the targetthe target

Near-field/Far-field imaging or bothNear-field/Far-field imaging or both Determine the optimal wavelength rangeDetermine the optimal wavelength range If IR, deal with the challenges of IR detection If IR, deal with the challenges of IR detection

(sensitivity, water vapor absorption, window (sensitivity, water vapor absorption, window material, …)material, …)

T. Sen; 10/18/2007 ODR for Hadron colliders

Choice of windowChoice of window

Quartz has almost Quartz has almost no transmission no transmission between 10 and between 10 and 50 microns. 50 microns. Might work for Might work for RHIC RHIC (~140microns)(~140microns)

Diamond would Diamond would be the material of be the material of choice for IRchoice for IRCourtesy: FLASH

T. Sen; 10/18/2007 ODR for Hadron colliders

Goals for Tevatron Goals for Tevatron measurementsmeasurements

Install ODR monitor in 2008 shutdownInstall ODR monitor in 2008 shutdown Measure two beam parameters with Measure two beam parameters with

good reproducibility for a single beam good reproducibility for a single beam Either beam size and beam positionEither beam size and beam position OROR Beam size and beam divergenceBeam size and beam divergence Measurements in both planes ?Measurements in both planes ? Measure parameters for several Measure parameters for several

bunchesbunches Update measurements every N turnsUpdate measurements every N turns

T. Sen; 10/18/2007 ODR for Hadron colliders

Pros and Cons of ODR in Pros and Cons of ODR in the LHCthe LHCPros.Pros.

Non-invasiveNon-invasive Beam size measurement near the IP on both sides, hence Beam size measurement near the IP on both sides, hence

beam size at the IP beam size at the IP Measurement itself will not be influenced by optics errorsMeasurement itself will not be influenced by optics errors This 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. A tomographic reconstruction of transverse phase space may A tomographic reconstruction of transverse phase space may

be possible from measurements over several turns. be possible from measurements over several turns. ConsCons Slower than synchrotron light monitor. Signal will have to be Slower than synchrotron light monitor. Signal will have to be

integrated over several bunches.integrated over several bunches. Errors associated with the measurement are not well known Errors associated with the measurement are not well known

at the moment. Installing a device in the Tevatron would at the moment. Installing a device in the Tevatron would determine the limits of resolution with this device.determine the limits of resolution with this device.

The ODR monitor would be installed between the TAS and The ODR monitor would be installed between the TAS and the 1st quad. Impact on the machine-detector interface needs the 1st quad. Impact on the machine-detector interface needs to be better understood. to be better understood.

T. Sen; 10/18/2007 ODR for Hadron colliders

Major LHC issuesMajor LHC issues What are the major benefits of imaging What are the major benefits of imaging

close to the IP?close to the IP? How do the errors associated with the ODR How do the errors associated with the ODR

measurement compare to the errors from measurement compare to the errors from propagating the synchrotron light monitor propagating the synchrotron light monitor measurement in the arcs to the IP?measurement in the arcs to the IP?

How fast can the ODR measurements be How fast can the ODR measurements be made?made?

What is the level of synchrotron radiation What is the level of synchrotron radiation background at the ODR target?background at the ODR target?

T. Sen; 10/18/2007 ODR for Hadron colliders

Next StepsNext Steps Design ODR setup in the Tevatron – Design ODR setup in the Tevatron –

E0 preferable. E0 preferable. Develop a collaboration with US labs Develop a collaboration with US labs

and CERNand CERN Present proposal to the LARP Present proposal to the LARP

collaboration for funding a LARP task collaboration for funding a LARP task (April 2008)(April 2008)

Proceed with experiments Proceed with experiments Develop ODR facility for the LHCDevelop ODR facility for the LHC Determine potential for future Determine potential for future

machines: muon collider, ILC,…machines: muon collider, ILC,…