Estimation of the neutron back-scatter for forward calorimetry upgrade

Contents:

Objective

• Estimation of the neutron back-scatter for forward calorimetry upgrade for a number of scenarios:
  • Phase II configuration of the EE forward calorimeter ( Shashlik design of 20 cells of 4mm W plates replacing EE but covering the same pseudorapidity range out to 3.0 )
  • A new HF calorimeter that can be treated as a block of W or Fe covering 3.0 < |η| < 4.6 with front face at 6.625m (Up-close HF W/Fe calorimeter option)
  • Same as above but with the front face at 3.964m (Very close HF W/Fe calorimeter option)

Studies with different CMS geometries

Current CMS geometry with a new HF at 6.625m

Add a W/Fe block at 6.625m, since TOTEM detector starts at Z=7.526m, so I added W from Z=6.625 - 7.526m i.e. 90cm wide and radius around 60-70cm (notice it is of conical shape). In addition to this, in front of W/Fe-HF, we would put a Polythene layer - 20cm wide same as in front of current HF position.

Neutron and Photon Flux maps

	Current CMS	Current CMS + W-HF at 6.625m	Current CMS + Fe-HF at 6.625m
Neutron maps
Photon maps

Comparison with current geometry:

	WHF/Current	FeHF/Current	WHF/FeHF	WHF-FeHF
Neutron Fluence
Neutron Fluence Ratio in tracker				-
Neutron Fluence Ratio in forward region				-
Photon Fluence
Photon Fluence Ratio in tracker				-
Photon Fluence Ratio in forward region				-

Current CMS geometry with a new HF at 4m

Add a W/Fe block at 4m with 1.5m width. A cylindrical shape has been added with 50cm for the outer radius and the inner radius of the cylinder is same as the beam pipe in those regions. In addition to this, in front of W/Fe-HF, we would put a Polythene layer - 20cm wide same as in front of current HF position.

Neutron and Photon Flux maps

	Current CMS	Current CMS + W-HF at 4m	Current CMS + Fe-HF at 4m
Neutron maps		-	-
Photon maps		-	-

Comparison with current geometry:

	WHF/Current	FeHF/Current	WHF/FeHF	WHF-FeHF
Neutron Fluence
Photon Fluence

Current CMS geometry with EE replaced by Shashlik

Replace the EE by a Shashlik EE with either W or Pb and LYSO. The PbWO4 EE material is replaced by material with average composition and density of a Shashlik detector. These detectors are shorter in z than the PbWO4 EE, the bounding plane is moved so that the total length of active EE and EE electronics is the same, i.e. the EE electronics region becomes longer. The ES and it's support structures has been removed (replaced by air). The polyethylene moderators upstream of ES and EE are still present.

Neutron and Photon Flux maps

	Current CMS	W+LYSO EE	Pb+LYSO EE
Neutron maps
Photon maps
Dose maps

Comparison with current geometry:

	W+LYSO EE/Current EE	Pb+LYSO EE/Current EE	W+LYSO EE/Pb+LYSO EE
Neutron maps
Photon maps
Dose maps

Installing FLUKA

wget --user=me --password=my --no-check-certificate https://www.fluka.org/packages/fluka2011.2-linuxAA.tar.gz
setenv FLUPRO path/to/fluka
setenv FLUFOR g77 (optional)
tar -xzvf fluka2011.2-linuxAA.tar.gz 
make

mkdir ../FLUKAwork/
cp CMS_simulation_resp13.tar.gz .
tar -xzvf CMS_simulation_resp13.tar.gz

$FLUPRO/flutil/fff -b -N fieldi.f
$FLUPRO/flutil/fff -b -N lbqfin.f
$FLUPRO/flutil/fff -b -N lbqfld.f
$FLUPRO/flutil/fff -b -N litwod.f
$FLUPRO/flutil/fff -b -N magfld.f
$FLUPRO/flutil/fff -b -N mgdraw.f
$FLUPRO/flutil/fff -b -N mhcos.f
$FLUPRO/flutil/fff -b -N ubsset.f
$FLUPRO/flutil/fff -b -N usrmed.f
$FLUPRO/flutil/fff -b -N usrglo.f
$FLUPRO/flutil/ldpm3qmd -o CMSpp -m fluka fieldi.o lbqfin.o lbqfld.o litwod.o magfld.o mgdraw.o mhcos.o ubsset.o usrglo.o usrmed.o
$FLUPRO/flutil/rfluka -e CMSpp -N0 -M1 CMSpp

Here are some scripts for running over large number of events: https://twiki.cern.ch/twiki/bin/view/Sandbox/FlukaUsefulScripts