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 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.

(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

Electron Trajectories in Micromachined Dynodes/InsulatorsStack 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 AssembledStacks(R).Channel Width~200 m

Future of SEM Calorimeter Sensors

• Iowa/Fairfield Propose Constructing Prototype SEM sensor module with gain of 105, 8 cm x 8cm.

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.

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%.

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.

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.