Detectors

BeamCal is an electromagnetic sandwich calorimeter that uses Tungsten as absorber. It serves three major purposes:

1. Improving the hermeticity of the ILC detector by providing electron and photon identification down to polar angles of a few mrad. This is a specially challenging task due to the vast amount of deposited energy from the electron-positron pairs originating from beamstrahlung.
2. Reducing the backscattering from pairs into the inner ILC detector part and protecting the final magnet of the beam delivery system.
3. Assisting beam diagnostics. A fast luminosity signal will be provided by BeamCal. The detailed analysis of the shape of the energy deposition from pairs hitting the BeamCal grants access to parameters of the colliding beams.

The sensors of the BeamCal must be very radiation hard. The technologies under investigation are:

- polycrystalline CVD diamond (Chemical Vapor Deposition),
- single crystal CVD diamond,
- GaAs,
- radiation hard silicon.

Geometries:

Unit 14 mrad Graphite shield thickness mm 100 Absorber layer 1 X0 mm 3.5 Sensor layer mm 0.3 Readout plane /air gap mm 0.2 total X0 int 30 x/y/z position mm +24.2/0/±3595 Rinner (sensitive area) mm 20 Router* (sensitive area) mm 150 Rbeam_in** mm 15 θinner mrad 5.6 θouter mrad 41.7 Tilt mrad 7 ~ Weight of absorber and sensor (sensitive area) kg 144.4 Table 1: BeamCal geometries for different beam settings. * We assume an Anti-Detector Integrated Dipole field: the magnetic field is parallel to the outgoing beams. Optimized for low backgrounds. **Crossing angles of 14 or 20mrad require an additional hole in each BeamCal for the incoming beams.

 

Segmentation:

Unit 14 mrad 0.8 RM cell size Rings int 16 ΔR mm 8.125 Sectors int 8 of 45 degree Cells per sector int 160 Cells/layer int 1280 Blind area degree ±22.5 around incoming beam, rings with R>63.4 are complete (n > 6) Table 2: BeamCal segmentation.

 

 

LumiCal serves three major purposes:

1. Measuring the rate of Bhabha events at low angles. The well known Bhabha scattering cross section will allow the precise determination of the luminosity of the ILC. Achieving the desired precision of 10^-4 is a challenge.
2. Reducing background by acting as a mask.
3. Improving the hermeticity of the ILC detector by providing electron and photon identification down to polar angles of a few mrad.

The technology of a Si-W sandwich calorimeter is under investigation for the LumiCal.
One of the challenges for LumiCal is the needed mechanical precision. A laser based position monitoring system is under development for LumiCal.

Geometries:

Unit   Absorber layer 1 X0 mm 3.5 Air gap mm 0.1 Sensor thickness + pad metalization mm 0.320 + 0.020 Fanout thickness mm 0.4 Total plane thickness mm 4.355 Total X0 int 30 x/y/z position mm +15.9/0/2500 Rinner* (sensitive area) mm 76 Router (sensitive area) mm 280 θinner mrad 30.4 θouter mrad 111.5 Tilt mrad 7 Space for electronics (outside the plane) mm 4.5 Mass of the LCAL (1 arm) kg 211.319 Table 3: LumiCal geometry. *We assume an Anti-Detector Integrated Dipole field: the magnetic field is parallel to the outgoing beams. Optimized for low backgrounds.

 

Segmentation:

Unit   Pad design - std Azimuthal sectors int 48 Δφsec mrad 131 Radial sectors int 64 ΔR mm 1.76 pads/layer int 3072 Table 4: LumiCal segmentation (for 14 mrad crossing angle).

 

Pair Monitor is a layer of silicon pixel sensors in front of BeamCal to assist beam tuning.

It is designed to be located at the first layer of BeamCal.

Geometries:

Hole radius (Upstream) 1 cm Hole radius (Downstream) 1.8 cm Router (sensitive area) 10 cm Thickness of sensor layer 0.2 ~ 0.3 mm Tilt angle 7 mrad Pixel size 0.4 mm × 0.4 mm Total number of readout pixel 190000 Table 5: Geometry of Pair Monitor