Transcript Towards a Digital Hadron Calorimeter

A Digital Hadron Calorimeter ?
Vishnu V. Zutshi
NIU/NICADD
The proposal
Development of New Hadronic Calorimetery Technology
G. Blazey, D. Chakraborty, A. Dyshkant, M. Martin,
V. Rykalin, V. Zutshi
NIU/NICADD
A. Brandt, K. De, A. White, J. Yu
UTA
Arrive at a realistic cost estimate for one of these devices
From analog to digital




Eflow seems to be a promising option for
improving jet resolutions significantly
ALEPH and CDF have successfully used it
Requires a high granularity calorimeter
Digital hadron calorimeters: high granularity at
affordable price ?
General Considerations







Granularity (energy and resolving power)
MIP recognition
Absorber density (optimize shower lateral size)
Depth
Matching to EM calorimeter
Readout (2d preferred to strip type)
Minimal intrusions
Energy and position
Too much of a good thing?
Analog and Digital
20 GeV pions in SD
Single Particle Resolutions
On the software side of things



Prototype simulations:
try out different cell shapes
parameterized losses from test stand
hoping to do this in GEANT4 framework
Event generation and LC detector simulation
Eflow algorithm development
starting with the EM section
The Algorithm (cal-seeded)





Layer-by-layer clustering based on a search for
local maxima
Cluster definition based on nearest neighbour
Track extrapolation through the calorimeter
picking clusters in its path
EM/HAD. Charged/neutral discrimination
Understanding of errors involved with the
tracking and calorimetric measurements
clusters
hits
Sanity Checks
Initial concept (scintillator-based)
Four concentric layers of
towers (7 stacks of 6-12
cells to a tower) formed
with hexagonal cells.
Start with 9cm2 cell.
Initial concept (scintillator-based)

•
Conversion to current:
VLPC’s
APD’s
MRS’s
PMT’s
Cost per channel v/s S/N
Test stand
Cell with WLS fiber irradiated by a radioactive or LED
WLS fiber connected to clear fiber which is connected to
a photodetector (PMT’s, VLPC’s etc.)
Output measured by a Pico ammeter
Test goals
TOP VIEW
Find minimum area/thickness of cell
Find minimum length of WLSF
Measure signal losses
at the WLSF to clear
fiber transition
With VLPC readout
MIP signal
Ch21,7.5K,6.2V,3.9V,near end
100
80
60
40
20
0
1 59 117 175 233 291 349 407 465 523 581 639 697 755 813 871 929 987
9mm thickness,0.5mm
fiber,2optical connectors
120
Initial concept (gas-based)






GEM approach
Developed initially for MSGC’s
Can be used with printed circuit readout
GEM’s with gains above 104 and spark
probabilities < 10-10 have been developed
Reasonably fast operation
Relatively low HV
Initial concept (gas-based)
Issues/concerns (gas-based)







Cost of GEM layers
Lifetime/damage to layers
Effects of highly ionizing particles
Gas(es) ?
Mechanical stability of GEM gaps/supports
Cross-talk
…..
Summary





Single cell characterization studies have begun
GEM based feasibility studies starting soon
Event generation and simulation server ready
Setting up for GEANT4 based prototype
simulation studies
Eflow algorithm development underway