1. WBS 1.05 Commissioning Detector Specifications & Design
Sven Vahsen
University of Hawaii

2. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
Talk Outline
Intro
US Project Scope
SuperKEKB commissioning schedule & Phases
Pre-prototype test results & Final Designs
Support Structure
PIN diode system
TPC fast neutron detectors
Summary
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

3. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
US Project Scope
Lead design, simulation, DAQ integration (off-project)
Construct support structure
Prototype & construct PIN-diode radiation dose monitoring system
Prototype & construct micro-TPC neutron monitoring system
Perform acceptance tests at KEK
Part of
US Belle II
Project
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

4. Latest Belle II Schedule
Key dates:
Phase I (No QCS, No Belle Detector): Jan 2015
Phase II (QCS, Belle, no VXD): Feb 2016
Phase III (QCS, Belle, VXD): October 2016
(This plan has changed repeatedly. Our mandate is to be ready for any commissioning scenario.)
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

5. Commissioning Detector Configurations
Phase I
Main task is vacuum scrubbing of beam pipe.
No collisions. Belle will not roll-in.
Support Structure and PIN diode system needed.
2 TPC prototypes will be deployed.
Phase II
Belle rolled in.
No VXD detectors.
8 Final TPCs needed.
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

6. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
Support Structure
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

7. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
Mechanics
Hawaii designs + builds phase I mechanical mounting structure
Lead: Rosen
(German VXD group + KEK taking on mechanical design for PXD/SVD/BGO mounting in phase II)
Phase I
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

8. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
PIN Diodes velcroed to beam pipe (not shown)
TPCs and other systems attached to fiberglass unistrut structure
simple, (very) inexpensive
can be reconfigured in minutes
non-magnetic
low activation
TPC
BGO
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

9. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

10. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
PIN diode system
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

11. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
PIN Diode System
Phase 1
Proposed diode pair positions
Phase 2
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

12. Dose Monitoring System
Lead: David Cinabro (Wayne State)
Use PIN diodes, Siemens SFH 206K PIN, to measure ionizing radiation dose
Inexpensive & robust
Successfully used in for ~10 years and integrated a dose of < 3 Megarads.
Every 2nd diode (in phi) coated with gold-paint
Allows separating dose from charged particles and xrays
CLEO Measurements
Synchrotron fan
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

13. PIN Diode System Prototyping
Commercial preamp and readout boards
(from Cremat)
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

14. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
Prototype System
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

15. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
Final System
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

16. DAQ for final system (off project)
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

17. TPC fast neutron detectors
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

18. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
Motivation for TPCs
Neutron Backgrounds
Difficult both to predict & measure accurately, caused problems already for Belle and Babar
Will be critical for Belle-II operation and lifetime
KLM deadtime, ECL electronics lifetime, iTOP photocathode lifetime
Idea: neutrons produced at specific loss-positions along the beam-line. Fast neutrons preserve directional information and can be directionally reconstructed. Use them to “image” loss spots.
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

19. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
How TPCs will be used
Commissioning phase II: He-3 tubes and micro-TPCs in dock space
Complimentary detectors
TPCs image direction of incoming fast neutrons, but detected rate is low
He-3 tubes measure rate of thermal neutrons, which is high
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

20. Recoil angle in Backward TPCs
Directional detection
motivation
Isolate neutrons coming directly from beam lines (rather than re-cattered)
Measure neutron flux versus polar angle (beam line position)  validate/tune simulation
Correct rates, but low MC statistics
nominal beams: RBB HER dominates
 measure
Run single beams
no RBB
measure Touchek
vacuum bump  measure Coulomb
Higher statistics & re-normalized
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

21. TPC Pre-Prototypes July 2013: Larger volume & less plastic
5 x higher neutron detection efficiency
10 x lower background rate
Used for ~2 years of detailed performance measurements
Used to demonstrate neutron detection with higher efficency
Performance of these detectors studied in great detail, well understood
Commissioning Detector TPCs : further scale-up in size to increase neutron detection efficiency
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

22. Demonstration of Directional Neutron Detection
Source Absent
He-recoil measured in HeC02 gas at p=1atm
L ~ 4 mm
E ~ 400 keV/c2
Mean direction of nuclear recoils corresponds to neutron source location
Source Present
Nuclear recoil
Incoming neutron
Scattered neutron
neutron
source
Clear excess & peaks in expected direction!
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

23. Angular and Energy Resolution, Nuclear Recoils
Po-210 α-source inside vacuum vessel. How well can we locate it?
HeC02 at p=1atm
σϕ= 1.0° α
σθ = 2.2°
Selected events clearly point back to a single source
No BG after good-track selection
consistent with σφ,θ detector ~1◦
July 2013 Sven Vahsen
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

24. Angular resolution versus “track size”
Analytical “prediction”:
σϕ~ σPOINT/(L√N)
The above allows us to extrapolate our results to other energies and gas pressures
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

25. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
Technical Status
Pre-prototypes of micro-TPCs have met and exceeded all Key Performance Parameters
Documented in Technical Design Report
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

26. Final TPC Prototype Design
Sensitive volume
Field cage
Charge amplification (GEMs)
Charge Detection
(Pixel Chip)
Aluminum vacuum vessel
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

27. Final TPC Prototype Construction
Design finalized
Two final prototypes are in production
Testbeam in 2014.
Install two at KEK fall 2014, eight in 2015.
Vacuum vessel
Field cage assembly
Final DAQ board
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

28. TPC Prototype Testing: Ongoing
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

29. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
Conclusion
WBS 1.5 Technical Designs are Mature
Detector (PIN diodes and TPCs) performance demonstrated with (pre-)prototype systems
Satisfy all KPPs
Final systems: Same detections principles, scaled up
More channels for PIN diodes
Larger sensitive volume for TPCs
Project Ready for CD-2/3
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3)

30. Sven Vahsen, Belle II Directors Review (Pre CD-2/3)
BACKUP SLIDES
16-17 January 2013
Sven Vahsen, Belle II Directors Review (Pre CD-2/3) 30

31. Recoil angle distribution in Forward TPCs
Correct rates, but low MC statistics
nominal beams: RBB LER dominates
 measure
Run single beams
no RBB
measure Touchek
vacuum bump  measure Coulomb
Higher statistics & re-normalized

32. BEAST Subsystem U.S. Contributions  dedicated talks
PIN diode dose monitoring system (Wayne State)
TPC directional fast neutron detectors (Hawaii)
 dedicated talks
Non-U.S. Contributions
BGO crystal luminosity monitors (NTU)
He-3 tube thermal neutron detector (Victoria, Canada)
PXD, SVD ladders, beam abort, synchrotron spectrum measurements: VXD groups (Bonn, MPI etc)

33. BEAST DAQ & Control Stand-alone BEAST DAQ proposed
~1Hz pseudo-events
Independent of Belle II
Phase I

34. Introduction
Commissioning detector will characterize radiation near SuperKEKB interaction point during beam commissioning.
Sub-systems supplied by a number of Belle II institutes, mounted on common mechanical support structure.
WBS 1.5 captures U.S. contributions to this effort
“BEAST” - KEKB commissioning detector in 1998 – effort led by U. Hawaii

35. Commissioning Detector Objectives
Determine if dose rate safe for Belle II roll-in and later operation at design luminosity (Belle I: hole in beampipe and damage to silicon vertex detector)
Provide real-time measurements of luminosity and backgrounds (needed by SuperKEKB during beam commissioning)
Validate Belle II beam background simulation (Distinguish different beam background sources (Touschek, Radiative Bhabha, Beam-gas, Synchrotron)
System tests for Belle II (Beam abort system, moveable mask positions, pixel detector cooling, inner detector occupancies)