Imaging the LHC beamImaging the LHC beamTanaji SenTanaji Sen

Accelerator DivisionAccelerator Division

Prospects for the LHC upgrade Synchrotron Radiation Optical Diffraction Radiation

December 13, 2006

Early separation – D0Early separation – D0

D0 D0

TripletTriplet D1D1

Early separation dipoles D0 placed inside the detector Beams collide with no crossing angle (D0 less than 3.75m from IP) or with a small crossing angle (D0 more than 3.75m from the IP). Luminosity loss due to crossing angle much smaller

Issues Integrating the dipoles into the detectors CMS and ATLAS Energy deposition in the detectors Impact of a few parasitics at small separations (< 4 σ) Choice of magnet technology: NbTi or Nb3Sn (shorter)

IP

Usable spectrumUsable spectrum

Quartz windows are transparent between 200 – 2500 Quartz windows are transparent between 200 – 2500 nm. nm.

CCD cameras operate in the range 200-1100 nmCCD cameras operate in the range 200-1100 nm

Synchrotron Radiation Synchrotron Radiation SourcesSources

Long Magnet – Long Magnet – bend angle bend angle θθ>> >> 1/1/γγ

Characteristic Characteristic λλcc = = 44πρπρ/(3/(3γγ33) = 58nm ) = 58nm for D0 dipole in for D0 dipole in LHC at 7 TeV; LHC at 7 TeV;

3004nm for 3004nm for Tevatron dipole at Tevatron dipole at 980 GeV980 GeV

Short Magnet Short Magnet θθ << 1/<< 1/γγ

Edge Radiation, Edge Radiation, λλee = L= Lee/(2/(2γγ22) < ) < λλcc

1/γ

θ/2

Long Magnet

Short Magnet

Edge Radiation

Synchrotron Radiation Synchrotron Radiation spectrumspectrum

D0 dipole in the D0 dipole in the LHC with field 4 T-LHC with field 4 T-m. m. ΘΘ=0.17mrad > =0.17mrad > 1/1/γγ = 0.13mrad. = 0.13mrad. So not a short So not a short dipole.dipole.

Critical frequency Critical frequency ννcc = 5.1x10 = 5.1x101515 Hz Hz

Half the power is Half the power is radiated at radiated at frequencies below frequencies below ννcc and half above. and half above.

Shape of spectrum Shape of spectrum is universal, at is universal, at other energies the other energies the curve is just curve is just shifted. shifted.

Angular spectrum - bodyAngular spectrum - body

Radiation in the visible range has a large Radiation in the visible range has a large angular spread. Difficult to use for imaging.angular spread. Difficult to use for imaging.

400 nm

Edge RadiationEdge Radiation Characteristic Characteristic λλcc

= L= Lee/2/2γγ22. If. If L Lee ~ ~ 40mm, 40mm, λλcc = 1nm = 1nm (deep UV)(deep UV)

Radiation from Radiation from the edges must the edges must not overlap, not overlap,

=> => θθ > 2/ > 2/γγ Extraction mirror Extraction mirror

should be 15should be 15σσ from the beam, from the beam, => B=12.6T for => B=12.6T for L = 15m. Too L = 15m. Too high a field and high a field and larger distances larger distances are unavailable. are unavailable. Beam

15σ

L

Diffraction Radiation - Diffraction Radiation - LayoutLayout

FDR

BDR

CCD

Filter

Polarizer

TargetProton beam

h Impact parameterp

Target

2Φ

Φ

Measured at KEKPhys. Rev Letters90, 104801 (2003)93, 244802 (2004)

LHC - Placing the LHC - Placing the targettarget

The impact parameterThe impact parameter

at 7 TeV, 1000 at 7 TeV, 1000 nmnm

Target should be clear of the beamTarget should be clear of the beam

Close to the IP,Close to the IP,

At 7 TeV, At 7 TeV, ββ*=0.25m, *=0.25m, λλ = 1000 nm, = 1000 nm,

Target can be placed at s ≤ 19m from IP !!Target can be placed at s ≤ 19m from IP !!

mmh 2.12

15h

s)*/(

DR spectrum and photon DR spectrum and photon yieldyield Characteristic Characteristic λλcc = 4 = 4ππh/h/γγ

At h = 1.2mm, At h = 1.2mm, λλcc = 2021 = 2021 nm nm

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=1010 nm,=1010 nm, ΔΔN = 1.81x 10N = 1.81x 1066

photons/bunch/turnphotons/bunch/turn

]53.1exp[48.0cd

dW

bNd

dWN

Exploration of Diffraction Exploration of Diffraction RadiationRadiation

May allow turn by turn and bunch by bunch May allow turn by turn and bunch by bunch monitoringmonitoring

Explore potential to measure:Explore potential to measure:

beam size, beam divergence, beam position beam size, beam divergence, beam position (from polarization, angular distribution, …) (from polarization, angular distribution, …)

Prospects at lower energies: Prospects at lower energies:

450 GeV 450 GeV ≤ E ≤ 7 TeV≤ E ≤ 7 TeV If no major obstacles, explore this as a new If no major obstacles, explore this as a new

LARP instrumentation task LARP instrumentation task

(FNAL joint with ANL(?), LBL, …)(FNAL joint with ANL(?), LBL, …)