March, 11, 2006 LCWS06, Bangalore, India Very Forward Calorimeters readout and machine interface Wojciech Wierba Institute of Nuclear Physics Polish Academy.

March, 11, 2006 LCWS06, Bangalore, India

Very Forward Calorimeters readout and

machine interface

Wojciech Wierba

Institute of Nuclear Physics Polish Academy of Science

Cracow, Poland


Contents

Instrumentation of Very Forward Region Mechanical design of Calorimeters Space for electronics & cooling Pads & strips designs Digital Calorimeter Channel occupancy & dynamic range Machine interface requirements Readout based on analog transmission Digital data transmission Readouts based on digital transmission


Instrumentation of Very Forward Region

BeamCal: 4 < θ < 28 mrad

LumiCal: 26 < θ < 82 mrad

PhotoCal: 100 < θ < 400 μrad


Mechanical design of LumiCal

Segmented silicon sensors interspersed into the tungsten half disks

Two half barrels to allow for mounting on closed beam pipe

The blue bolts support the heavy part of the detector, tungsten half disks

The red bolts carry only the sensors Holes for precision survey the sensors

position


Mechanical design of BeamCal

•Diamond-Tungsten Sandwich Calorimeter

•Two half-barrels placed just outside the beam

•Thickness of the tungsten absorber disks is one radiation length

•Space for the sensors is ~0.5 mm


Space for electronics

•There is a limited space for the FE electronics for the 300 mm outer radius of LumiCal

•Bolts for tungsten & sensors support takes additional space

•Si sensors online positioning needs place also


Pads & Strips Design

Both designs becomes very similar

Different number of electronic channels: Strips ~8000, Pads ~25000

Strips Pads


Digital Calorimeter

Very high segmentation ~10 000 channels per plane = 300 k channels for calorimeter

MC studies shows very good performance Preamplifiers, shapers, discrimators, zero

suppression = simple (?) readout electronics (no need of ADC’s)

Readout electronics have to be placed directly on the detector surface

This is a brand new idea, details should be worked out


Channel occupancy & dynamic range

•The LumiCal mean channel occupancy is round 20%•The BeamCal mean channel occupancy is even higher•The zero suppression will not work efficiently•The expected mean signal i one cell is ~25 MIPS•For good event reconstruction we will need 14-bit ADC


Machine interface

LumiCal can provide raw luminosity measurement after a bunch train – readout can be done in time slots between trains ~300 ms

Precision luminosity can be calculated later (in order of seconds)

BeamCal should provide beam diagnostics information (σx, σy, σz and Δσx, Δσy, Δσz, xoffset, yoffset and Δxoffset, Δyoffset, Bunch rotation, N

particles/bunch) after a few bunches – readout should be done simultaneously with bunches every ~300 ns (~150 ns)

Beamstrahlung Pair Analysis needs fast algorithm


Possible readout designs

Analog transmission – simple, low heat dissipation, easy to maintenance – a huge number of cables, crosstalk, noise

Digital transmission – small number of digital links, no crosstalk on the transmission – complicated, high heat dissipation


Analog transmission

25000 analog cables (coaxial or TP) needs ~30 mm round the LumiCal (can be reduced using multilayer flex PCB)


Digital Transmission LVDS link

Current speed – 0.6 Gb/s Up to 10 m


Data stream for Forward Calorimeters

3000 bunches i one train – 1 ms

Break between trains – 300 ms

Number of channels – 25000

10 bit ADC

Amount of data per train – 0.75 Gb

Transmission during train – 750 Gb/s - ~1250 links

Transmission during break – 2.25 Gb/s - ~4 links

>>


Possible readout solutions

ADC in each channel – expensive and space on chip consuming

One ADC for a group of channels – cheaper, needs S/H, MUX and faster ADC

Analog pipeline with ~3000 cells and 12 (14) bits accuracy over 300 ms is not a easy project, but the number of ADC can be reduced by a factor of ~300

Parallel conversion

Multiplexed ADC

Analog pipelined


Conclusions

Number of channels and ADC resolution is essential to chose the readout solution

Digital data transmission over the break between trains possible only for LumiCal

The BeamCal should be read out simultaneously with bunches

DAQ for the Forward Calorimeters has to read out each bunch crossing and the readout philosophy

is different to the rest of Detector DAQ

March, 11, 2006 LCWS06, Bangalore, India Very Forward Calorimeters readout and machine interface Wojciech Wierba Institute of Nuclear Physics Polish Academy.

Documents

india space

india instrumentation

india digital calorimeter

digital transmission

poland slide

rad slide

stripspads slide

adc slide