1. Backward Calorimetry For SuperB
____ _____
May 13, 2009

2. Introduction
The original design for the backward endcap calorimeter consisted
of tiles yielding readout channel
Since on average only 1 particle is expected in the backward EC
the segmentation can be substantially reduced
Instead of using tiles one can use strips
Dave Hitlin suggested to use spiral-shaped strips
The new design will use 3 different shapes of strips:
Right-handed spirals
Left-handed spirals
Sectors
The 3 layers will alternate

3. SuperB: Baseline Design
Rear
endcap 3

4. Scintillator Planes
Alternate 3 different strip shapes 8 times 24 layers in total
There are 48 strips per layer yielding 1152 strips
Due to the different strip shapes layer need to be mounted completely
 no split into halves
The sectors overlap 7 left-handed and 7 right-handed spirals

5. Strip Fabrication
For practical reasons it is best not to produce individual strips
but to start out with a rectangular scintillator sheet
First outer and inner spiral edges
as well as inner and outer circular edges
Next we mill 5 grooves along the spiral
lines to produce 6 strips
We leave small bridges uncut so that the
6 strips are connected in a few places
 we need to measure the cross talk
to decide size of the bridges
Gaps are filled with white diffuse reflector
This procedure provides mechanical stability for each sheet
8 such sheets make one layer

6. Strip Readout The scintillator strips are 3 mm thick
At the outer edge the strips are 9.8 cm wide, at the inner edge 4.1 cm
In the center a 1mm deep spiral-shaped
groove is cut into which the WLS fiber
is inserted
A SiPM (MPPC) is mounted at the outer edge
A mirror is positioned at the inner edge of
the fiber
Thin boards with traces are placed on the
outer edge to which the SiPM pins
are soldered to
SiPM
mirror

7. R&D in Bergen We have started to test SiPMs and other
pixelated avalanche photomultipliers in
our laboratory
Spectrum with light pulser and 106Ru source
MEPHI/PULSAR
1156 pixels
gainSiPM~4105
1pe
2pe
3pe
pedestal
MIP=4-5 pixels
(33 cm2)
4pe
5pe

8. R&D in Bergen
We have started gain and MIP measurements

9. Conclusion The new design reduces the number of channels to 1152
With the spiral design (sectors overlap 7 left-handed and 7 right-
handed spirals) the position of the shower should be determined
rather precisely
In this design the entire calorimeter is built in one piece
 it cannot be removed without removing the beam pipe