Y.Onel, University of Iowa D.R.Winn, Fairfield University
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Transcript of Y.Onel, University of Iowa D.R.Winn, Fairfield University
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New Calorimeter Technologies for NLC
(a) Secondary Emission Calorimeter Sensors(b) Cerenkov Compensated Precision Calorimetry
Y.Onel, University of Iowa
D.R.Winn, Fairfield University
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(a) Secondary Emission Sensor Modules for Calorimeters
• Basic Idea:A Dynode Stack is an Efficient High Gain Radiation Sensor
- High Gain & Efficient (yield ~1 e/mip for CsSb coating)- Compact (micromachined metal<1mm thick/stage)- Rad-Hard (PMT dynodes>100 GRads)- Fast- Simple SEM monitors proven at accelerators - Rugged/Could be structural elements (see below)- Easily integrated compactly into large calorimeters
low dead areas or services needed.
SE Detector Modules Are Applicable to:- Energy-Flow Calorimeters- Polarimeters- Forward Calorimeters
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(a) Secondary Emission Sensor Modules for Calorimeters
Basic SEM Calorimeter Sensor Module Form:
“A Flat PMT without a Photocathode”:- The photocathode is replaced by an SEM film on Metal.- Stack of 5-10 metal sheet dynodes in a metal “window”-ceramic wall
vacuum package about 5-10 mm thick x 10-25 cm square, adjustable in shape/area to the transverse shower size.
- Sheet dynodes/insulators made with MEMS/micromachining techniques are newly available, in thicknesses as fine as ~0.1 mm/dynode
- Ceramic wall thickness can be ~2mm, moulded and fired from commonly available greenforms (Coors, etc.)
- Outer electrodes (SEM cathode, anode) can be thick metal, serving as absorber and structural elements.
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(a) Secondary Emission Sensor Modules for CalorimetersSchematic of SEM Calorimeter Sensor
Module
brazed ceramic insulators
10 mil HV insulator (polymer)
signal (male)
signal (female) -optional for stacking
film bias resistor chain
1.8 mm thick Cu
HV connector
HV female socket (optional for stacking)
stackable
-2kV
signal out6 dynodes (200 µm thick @ 0.8mm spacing) 50ž
2 silicon micro channel plates
Cs3Sb SEM Surface
1cm
15 cm
top view
ceramic
Cu plate
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Electron Trajectories in Micromachined Dynodes/InsulatorsStack of 8 sheet dynodes
Note: dynode thickness ~ 100 microns
Thickness:<2mm
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Micromachined Metal Cs3Sb Coated Dynodes – available up to 30 cm diameter
View Down Single Channel of Stack,Showing Offset
Mesh Dynode(L)And AssembledStacks(R).Channel Width~200 m
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Future of SEM Calorimeter Sensors
• Iowa/Fairfield Propose Constructing Prototype SEM sensor module with gain of 105, 8 cm x 8cm.
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b) Cerenkov Compensation Precis
• Basic Idea:Cerenkov Light is most sensitive to electrons (photons)
Ionization sensitive to neutrons, hadrons, electronsUse these 2 measurements to correct calorimeter energy – stochastic & constant terms
- Detect both Cerenkov Signal Ec and Ionization Ei on the same shower.- For pure e-m showers, normalize the detected energies so that Ei = Ec = Eem.- For hadrons, only when only 0 are produced does Eh ~ Ei ~ Ec. - As Eh fluctuates more into n, +-, etc., Ec decreases faster than Ei. - On an Ec vs Ei scatter plot, the fluctuation is correlated/described by a straight line with
slope a<1, from which the constant is defined by a = /(1+).- The Ec vs Ei correlation yields an estimate of the compensated E as:
Ecomps = Ei + (Ei-Ec),where the constant is different for each calorimeter material/design.For electrons, Ecomps = Ei = Ec, since (Ei-Ec) = 0
- No “suppression” needed for compensation, thus more active material can be used, up to 100%, thus reducing the stochastic term.
- Two independent measurements enable tuning the constant term to near zero.
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Cerenkov Compensation MC Results• GEANT MC Checked by reproducing data:
- pions in Lscint (10% stochastic, 10% constant term, FNAL E1A)- pions in PbGlass (35% stochastic, 10% constant – Serpekov)- e in PbGlass (5% stochastic)- e in Cu/Quartz fibers(1.5%) (80% stochastic, 1% constant – CMS)
• Infinite media (LAr, Lscint, BaF2, NaI(Tl)), counting detected ionization and Cerenkov light yields (filters for scintillators): E/E ~ [11%-16%] E-1/2, with constant terms <1%.
• Model Cu absorber Sampling Fiber Calorimeter15% 0.8 mm clear fibers, 35% 0.8 mm scintillating fibers:- E/E ~ 18-20% E-1/2, with a constant term <0.5%.
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Potential Applications in NLC
• Compensating E-M & Hadron Calorimeters- CMS experience: combined crystal em + compensated hadron Calorimeter:
hadrons E/E ~ 90-100%E-1/2 + 3-4% - unacceptable for NLC performance.
- To correct a crystal em+hadron system, Add a 2nd wavelength filtered Cerenkov photodetector to each crystal to compensate the crystal e-m calorimeter. Combined em+hadron Resolution should reach resolution of compensated hadron alone.
- To correct any highly non-compensated em calorimeter, add some Cerenkov (or electron-sensitive) detector.
• High Precision Sampling Hadron Calorimeter- MC indicates that E/E ~ 20%E-1/2 + <1% practical
- Energy-Flow possible with Clear & Scintillating “bricks”
read-out with WLS fibers, similar to ATLAS, CMS schemes.
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Future Work on Cerenkov Compensation
• Iowa/Fairfield are proposing to beam-test crystal compensation. Preliminary Tests at CERN this July/August. Need support for full test.
• More Detailed GEANT4 MC of possible fiber and energy-flow designs in progress.