Transcript Explicitly Radiation Hard Fast Gas Cerenkov Calorimeter as Luminosity Monitor (Task#56) Characteristics •Explicit radiation hardness •Silent to low energy e± and gamma •Fast (50-100ps) •Energy resolution ~10% Satisfies the requirements.

Explicitly Radiation Hard
Fast Gas Cerenkov
Calorimeter
as
Luminosity Monitor
(Task#56)
Characteristics
•Explicit radiation hardness
•Silent to low energy e± and gamma
•Fast (50-100ps)
•Energy resolution ~10%
Satisfies the requirements of
the Luminosity Monitor.
Explicit radiation hardness…
… explicit radiation hardness is hard to
achieve with atoms, especially those in
solid form – damage remains in the active
medium and can be achieved only with
metal and gas.
Gas+Metal
… silent to low energy(<10MeV) e±
and gamma…
• Index of refraction for gas
differs by very small
fraction from unity (i.e.
n=1+δ)
Xe: δ =.007
Isobutane: δ = 0.019
etc.
•Threshold energy for emission of Cerenkov radiation
Eth 
n
n2  1
eisobutane
th
E
m0c 2 
m0c 2
2
 9.8MeV
…comfortably above radiactivation energy
“Lasagna” (“accordion ”) geometry
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Simulated performance I
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Simulated performance II
• Time resolution of 50-100ps (pancake of
light commoves with shower which has
spread of the order of cm )
• ~10% of energy resolution (comparable
with HF quartz fiber calorimeter at CMS)
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How do you collect signal every 1.4ns
from such calorimeter?
• Use mirror to redirect photons off shower axis in
order to minimize noise in PMT
• Hamamatsu has very fast PMT – 100ps rise time;
goes down to 200nm! Pricy, but such superior
performance can be lowered for the sake of price…
• FPGA – capable of digitizing data at rates of GHz,
allow parallel readout, storage of the train of
events, etc…Inexpensive!
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Mechanical manufacturing?
• “Lasagna” design is very robust – no need
for complicated milling, machining, can be
assembled from on-shelf components metal plates, bars, shim;
• The only critical part is shim surface and
its aluminization.
Current status
• Geometry is understood; generic design is developed;
• Expected performance (G3) - 10%/√E, 100ps, rad.hard, silent to
noise ;
• High quality of s.s. shim is achieved;
• …technology is being developed (in UA) for mass manufacturing;
• …as well as quality control of optical surface…
• Final design … depends on where monitor will be placed;
• GEANT4 simulation of this particular geometry is almost completed
(I need to get rid of some minor bugs)
• Find optimal gas (minimize scintillation light), geometrical
parameters - gas/absorber ratio,
• It is feasible to make and test prototype at H2 facility at CERN
(maybe somewhere else?)
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