Secondary Emission Calorimetry R&D

1. Secondary Emission CalorimetryR&D Burak Bilki (for David Winn) University of Iowa Argonne National Laboratory CHEF2013, Calorimetry for High Energy Frontier April 22-25, 2013 Paris, France

2. Why Secondary Emission Ionization Calorimeters? • Secondary Emission (SE) signal: SE surfaces inside em/had showers: • SE yield  Scales with particle momentum • e-: 3 <  <100, per 0.05 <e-<100 keV(material dependent) •  ~ 0.05 - 0.1 SEe- per MIP • SE is:Rad-Hard + Fast • a) Metal-Oxide SE PMT Dynodes survive > 100 GigaRad • b) SE Beam Monitors survive 1020MIPs/cm2 • Ex: ~60-240 SEe- per 100 GeV pion shower w/ MIPs alone • BUT SEe- Must be Amplified! Exactly like photoelectrons (p.e.)!

3. In CMS Hadron Forward Calorimeter Phase II Upgrade Framework 25 X0 Forward EM Calorimeter 1 X0 W/Fe + SEe Sensor ~ 1.5 – 2.5 cm thick An SEe is statistically exactly like a p.e. g~105–106 e per SEe (SEe as generated by shower particles) (just like p.e. gain from collected photons w/ g=105-6) A) Muon MIP: ~ 0.1 SEe- per sample module x 25 ModulesMIPSignal: We predict ~2.5 SEe/Muon (in 25 X0EM module) but we measure ~8x this in Test Beam! B) EM Showers: ~900 shower electrons/GeV yields 45-90 SEe/GeV NB: Lower Estimates! MIP SE, not true SE from particles

4. SEe Dynodes: a) Etched Metal Sheets Hamamatsu Dynodes 15 cm now ~50 cm Already diced from large sheets

5. SEe Dynodes: b) Metal Screen Dynodes: 15D - g~105 MESH DYNODE VARIANTS Dn-Dn+1: 0.9 mm C-C mesh: 13 µm Wire diameter: 5 µm

6. Beam Tests of SE Sensor CERN SPS, Oct. 2011 Mesh PMT and Base Facing Downstream Photocathode Reverse Bias 19 Stage Mesh 3 cm Pb 100 GeV e- We Expect ~500 Shower electrons to Cross Mesh ~25-50 SEeassuming all shower e = MIPs

7. BEAM TEST: 100 GeV electrons 3 cm Pb ~ 5 X0Radiator ~ Shower Max downstream the mesh PMT w/ photocathode turned off CERN SPS, Oct. 2011 • PRELIMINARY! • Fluctuations High! • PMT Dia ~ Shower Dia • Beam not centered • NOTE µ MIP: • Detection Eff~10% • Response ~1-2 “SEe” Peak corresponds to ~40 SE electrons (mesh stack gain ~105)

8. 100 GeV Electrons – SE Mode CERN SPS, Oct. 2011 ~4 X0 Charge > 160 fC cut applied. (1 pe ~ 160 fC) Scales with X0. Note: Shower not laterally contained!

9. 80 GeV Electrons – SE Mode CERN SPS, Oct. 2011 Charge > 160 fC cut applied. (1 pe ~ 160 fC) Scales with X0 Note: Shower not laterally contained!

10. SEe Efficiency with Muons CERN SPS, Oct. 2011 Below Thresh. Muon Efficiency ~80% (1 pe ~ 160 fC) Muons pass through the mesh dynodes (selected by the wire chambers)

11. SE Module Beam Test Using mesh dynodes from PMTs CERN SPS, Nov. 2012 51 53 52 Beam position (into the page) 2 datasets Selected with Wire Chamber 54 56 55 57 59 58 51, … , 59: PMT IDs

12. SE Module Beam Test 2-cm iron absorbers: X0 = 1.75 cm Molière Radius: 1.72 cm 80 GeV e- Beam Variable absorbers 0 – 9 X0 SE SE SE SE Shower not contained laterally or longitudinally  Results require estimates and approximations

13. SE Module Beam Test No upstream absorber 80 GeV e- Beam hitting 1-51 Efficiency ~ 41% Different measures of efficiency possible, here Charge > 45 fC (pedestal RMS) is chosen.

14. SE Module Tests – Preliminary Results Normalizing responses of different layers Example: Normalization of Layer 3 response to Layer 2 response using 7X0 sampling (Also works in the reverse order  next slide) Charge > 20 fC

15. SE Module Simulation Geant4 simulation of the SE module test beam setup: 80 GeV e- beam 19 stage mesh dynodes generate SE electrons (dynodes ~ sheets) Gain is simulated offline (106) Landau fluctuations are implemented offline Single parameter to tune: Efficiency of SEeproduction (mesh dynodes are simulated as solid sheets) 0 - 0.35% flat random

16. SE Calorimeter Simulation Using SE module MC tune 25 X0 sampling calorimeter 1.75 cm Fe absorbers 19-stage SE sensor ~ 2 cm Lateral size 1 m x 1 m Landau fit MPVs and MPV errors

17. Conclusions Secondary Emission calorimeter is radiation-hard and fast. Progressive beam test results are encouraging for better prototypes. More beam test needed  Next generation calorimeter prototype in preparation. SE calorimetry is feasible for large-scale applications. Large implementation options once the proof of concept is established (forward calorimetry for hadron/lepton colliders, beam monitors, Compton polarimetry for lepton colliders, etc. ).

18. Backup Slides

19. Secondary Emission Cartoon of Secondary emission as used in an accelerator beam monitor, and as would be used in a calorimeter. Electrons freed by ionization random walk into the surface oxide, a thickness typically 10-50 nm thick, over typically 1-2 µm in the underlying metal. A few escape into the vacuum, enhanced by an applied electric field, becoming “secondary electrons”. The yield g is given by the semiempirical Sternglass formula, one version of which is shown in the RHS of the figure, with L being the escape depth, Ep the particle energy and Ap the mass Proton SE yield vs Ep X200 peak-valley SE: ionization e- random walk to surface oxide (10-50 nm thick), from ~1-2 µm in the underlying metal, escape into t vacuum under applied E-field = “secondary e-” = SEe. SEYield gb-Semiempirical Sternglass L = Escape Depth, Ep, Ap = particle energy, mass

20. GEANT4: Cu Block, 1cm “plates”, 100 GeV e incident. Shower e+/- that cross the 1 cm “gaps” are binned in both energy and depth in Cu Shower +/- electron Energies

21. GEANT4: e’s in Cu 1 cm absorber Plates Count e+/- crossing gaps dNe/dE vs Shower e+- KE 10 GeV e • ~900 e+-/GeV • Cross 1cm Cu gaps ~Indep of Einc • Yields 45-90 SEe/GeV generated. • (assume all mips) Shower e+- energies crossing gaps 100 GeV e

22. SEe Detector Module Concept -HCal 3D Stackable x,y,z

23. Example SE: CERN LHC Beam Loss Monitor

24. Signal Generation from protons – DESY BPM Al2O3,TiO2 ~0.05 e- per MIP. Yet used as beam monitors: Rad Hard! Hadron Showers: Sub-mip Charged particles