LumiCal

LumiCal serves three major purposes:

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.
Reducing background by acting as a mask.
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:

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.
		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
R_inner^* (sensitive area)		mm	76
R_outer (sensitive area)		mm	280
θ_inner		mrad	30.4
θ_outer		mrad	111.5
Tilt		mrad	7
Space for electronics (outside the plane)		mm	4.5
Mass of the LCAL (1 arm)		kg	211.319

Segmentation:

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