endcaps of the CLIC detector Suzanne van Dam Supervisor André Sailer CERN 6 March 2014 Introduction Beambeam interactions Background incoherent pairs Scatter in forward region of CLIC detector ID: 353582
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Slide1
Reducing the occupancies in the calorimeter endcaps of the CLIC detector
Suzanne van DamSupervisor: André SailerCERN, 6 March 2014Slide2
IntroductionBeam-beam interactionsBackground incoherent pairs
Scatter in forward region of CLIC detector High occupancy in HCalSuzanne van Dam, 6 March 20142
CERN-THESIS-2012-223Slide3
Occupancy reductionSuzanne van Dam, 6 March 2014
3The high occupancy has to be reducedSupport tube can provide shieldingOptimize support tube material and thicknessSlide4
Suzanne van Dam, 6 March 20144
Simulation of occupancySimulate background for each geometryEstimate the occupancyNeed data from a few bunch trains (312 BX/train)Find number of particles passing through support tube
Correlated to occupancy
Need data from ~10 BXs
Geometrical adaptations to the detector model:
Introduce a scoring plane around support tube
Make support tube geometry variable
Slide5
Simulation of occupancySimulate background for each geometry
Estimate the occupancyNeed data from a few bunch trains (312 BX/train)Find number of particles passing through support tubeCorrelated to occupancyNeed data from ~10 BXsGeometrical adaptations to the detector model:Introduced a scoring plane around support tubeMade support tube geometry variable through text file
Suzanne van Dam, 6 March 2014
5Slide6
Contributions to occupancy
Occupancy per particle type:Photons and neutrons contributeCompare to number of hits from different particles in the scoring plane:Photons have a relatively large impactReflect this in the relation between hits in the scoring plane and the occupancySuzanne van Dam, 6 March 2014
6
Energy
deposits
in
HCal
endcap
Hits in scoring
planeSlide7
Figure of meritTo minimize the occupancy, minimize neutron (n) and
photon (γ) hits (H) with a relative weight (w)Assume linear dependence on each particle typeThis can be expressed in a figure of merit (
FOM
):
W
eights follow from the ratio of:
Number of energy deposits above threshold and within timing cut in the
HCal endcap (
N);Number of hits in the scoring plane (
H).
Suzanne van Dam, 6 March 2014
7Slide8
EnergyEnergy spectrum for hits in the scoring plane
HCal endcap threshold is 300 keVSuzanne van Dam, 6 March 20148Slide9
Support tube materialIron
Suzanne van Dam, 6 March 20149
photons
neutronsSlide10
Iron based:IronStainless steel
Cast ironBorated steelSuzanne van Dam, 6 March 20149Support tube material
photons
neutronsSlide11
Iron based:IronStainless steel
Cast ironBorated steelNeutron moderating and absorbing:Pure polyethylene (PE)PE + Li2CO3PE + H3BO3 Suzanne van Dam, 6 March 2014
9
Support tube material
photons
neutronsSlide12
Suzanne van Dam, 6 March 20149
Support tube materialIron based:IronStainless steelCast ironBorated steelNeutron moderating
and absorbing:
Pure polyethylene (PE)
PE + Li2CO3
PE + H3BO3
Short radiation length:
TungstenLead
photons
neutronsSlide13
Combine materialsPolyethylene for neutron shielding
Iron-based materials for photon shieldingTungsten for further photon shieldingTo shield both photons and neutrons, materials should be combined.Suzanne van Dam, 6 March 201410Slide14
Combine materialsPolyethylene & stainless steel
Suzanne van Dam, 6 March 201411
T
otal
thickness
of support tube 100 mmSlide15
Combine materialsPolyethylene & stainless steel
Tungsten & stainless steelSuzanne van Dam, 6 March 201411
T
otal
thickness
of support tube 100 mmSlide16
Summary and conclusions
The high occupancy due to incoherent pairs in the HCal Endcap is caused by neutrons and photonsPhotons have relatively more impact on the occupancyMinimization of the occupancy is based on minimizing the number of particles passing the support tube Therefore a figure of merit is defined that reflects the higher impact of photons:Simulations show thatTungsten is suitable for photon shieldingPolyethylene is suitable for neutron shielding
To shield both neutrons and photons materials should be combined
A high contribution from photon shielding materials is needed
Suzanne van Dam, 6 March 2014
12Slide17
OutlookMaximize shielding by reducing inner radius of support tube
Use as much tungsten as structural strength allowsFor neutron shielding add polyethylene to a structure of tungsten and stainless steelSuzanne van Dam, 6 March 201413