1. Explicitly Radiation Hard Fast Gas Cerenkov Calorimeter
Luminosity Monitor
(Task#56)

2. Explicit radiation hardness
Characteristics
Explicit radiation hardness
Silent to low energy e± and gamma
Fast (50-100ps)
Energy resolution ~10%
Satisfies the requirements of the Luminosity Monitor.

3. 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

4. … 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
…comfortably above radiactivation energy

5. “Lasagna” (“accordion ”) geometry

6. Simulated performance I

7. Simulated performance II
Time resolution of ps (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)

8. 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!
Crossing by crossing readout is feasible!

9. 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.
Robust and inexpensive to build

10. 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?)