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BDSIM screenshots ● Green line is a photon. It passes through QD6 and QF5 and hits SF5. ● BH5 must have a window ● Holes would need to be drilled in yoke of SF5 for detection further downstream. This would affect the magnetic fields BH5 QD6 QF5 SF5 Possible Detector Locations
Citation preview
Location of the LW detector- Simulation of the LW signals
Lawrence Deacon RHUL ATF2 meeting August 23rd 2006 KEK
Possible Locations
● Between BH5 and QD6● Between QD6 and QF5● Further downstream
BDSIM screenshots● Green line is a photon. It passes
through QD6 and QF5 and hits SF5.
● BH5 must have a window
● Holes would need to be drilled in yoke of SF5 for detection further downstream. This would affect the magnetic fields
BH5
QD6
QF5
SF5
Possible Detector Locations
< QD6● Space is 0.55m
● Could fit aerogel Cerenkhov (detector we are currently using at ATF) if extra mirrors are used to reflect the cerenkhov light hoizontally before it is reflected down into the PMT
● Very difficult to fit current calorimeter in.
● Could limit detector choices.
● Laserwire signal between 2cm and 5cm from beamline
QD6 > QF5
● Laserwire signal would pass through gap between pole tips
● Bolt heads need to be shortened
QD6 > QF5
● Space is 1.6m – space required for BPM
● Can put larger detectors at this location
● Laserwire signal approx. 15cm from beam line
Simulations
● ATF2 laser wire simulated using BDSIM
Quadrupole Model
● Modelled in BDSIM as shown
● Red is iron● Green is copper (part
of coils)● Dimensions match
technical drawing
Simulation materials/ apertures● Beam pipe radius= 2.14cm (except in apertures)
● Beam pipe material is aluminium throughout (should be steel in drifts and copper in magnets?)
● Magnet material is Iron (small part of quad is copper)● BH5 is vacuum (window to allow photons through)
● Apertures between pole tips and coils in quarupoles
Simulation Apertures
Simulation Beam Parameters at Start of EXT
● Energy cutoff = 1MeV● Energy= 1.28GeV● SigmaE= 0.8 e-3● Horizontal emittance= 2.0 e-9● Normalized vertical emittance= 3.0e-9
Simulation Beam Parameters at Start of EXT
● Beta x = 7.328756752062● Beta y = 3.138666109153 ● Alpha x = 1.182561568783● Alpha y = -1.770354080712● From mad files (Mark Woodley, SLAC)
Laser Wire Parameters
● Position: extraction line at MW0X (between QD18X and QD19X)
● Wavelength= 532nm● Spotsize= 15 microns
Simulated e- Beam at Start of EXT/Laserwire
● Top: y ● Bottom: x● Left: start ● Right:at laserwire● Units: microns
Simulated Compton Scattered Photon Spectrum
● Photon spectum at laserwire IP
● Units: GeV● High energy cutoff
agrees with theory● Artificial cutoff below
1MeV
Laserwire Photons at IP
● Left: xp/yp● Right: x/y
Comparison of Detector Locations
● Particle distribution x y
● Left: <QD6● Right: QD6>QF5
Comparison of Detector Locations
● Left: primary particles Right:not primary particles
● Top: <QD6 Bottom: QD6>QF5
Comparison of Detector Locations● Secondary particles were scattered over large angles.
● Secondary particle number and energy could fluctuate more than that of primary particles
● Compared energy for different sampler (detector) sizes at both locations and
● Standard deviation in the energy/energy for different sampler sizes at both locations
● Statistics are from 10 shots with 1000 scattered photons each (will be higher will shorter wavelength laser).
● Assumed that detector is uniformly sensitive to edge. Further simulation required to include effects of mirrors etc.
Comparison Of Detector Locations● Energy per shot/ GeV● One shot scatters 1000
photons from e- beam. Increases with shorter laser wavelength. May go to shorter wavelength in future.
● Top: at < QD6● Bottom: at QD6<QF5
Comparison of Detector Locations● standard devation in
energy/energy
● Around 2.5% fluctuations and 9.5 GeV at <QD6 and 3.5% fluctuations and 8GeV at QD6<QFF
● Detector area should be 5m by 5cm to maximise signal?
Best Location● The difference in signal between the two locations is not
great
● More space in the second location provides more flexibility
● Laser wire signal is further from beam line at second location so more space is available
● The background at one location could be higher than at the other
● Will bolt heads may need to be shortened in QD6 for second location?
Future Work
● Simulate background● Compare simulations with ATF results● To do this the current detector must be calibrated● Test new detector setup● Try calorimeter● Try simulations with different e- beam optics● Simulate detector: lead, aerogel, mirrors.