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

(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

(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 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.

(a) Secondary Emission Sensor Modules for Calorimeters Schematic of SEM Calorimeter Sensor Module

Electron Trajectories in Micromachined Dynodes/Insulators Stack of 8 sheet dynodes Note: dynode thickness ~ 100 microns Thickness: <2mm

Micromachined Metal Cs3Sb Coated Dynodes – available up to 30 cm diameter View Down Single Channel of Stack, Showing Offset Mesh Dynode(L) And Assembled Stacks(R). Channel Width ~200  m

Future of SEM Calorimeter Sensors Iowa/Fairfield Propose Constructing Prototype SEM sensor module with gain of 10 5, 8 cm x 8cm.

b) Cerenkov Compensation Precis Basic Idea: Cerenkov Light is most sensitive to electrons (photons) Ionization sensitive to neutrons, hadrons, electrons Use 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.

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 Calorimeter 15% 0.8 mm clear fibers, 35% 0.8 mm scintillating fibers: -  E/E ~ 18-20% E -1/2, with a constant term <0.5%.

Potential Applications in NLC Compensating E-M & Hadron Calorimeters - CMS experience: combined crystal em + compensated hadron Calorimeter: hadrons  E/E ~ %E -1/ % - unacceptable for NLC performance. -To correct a crystal em+hadron system, Add a 2 nd 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.

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.