1. The UNH SVT Testing Facility: Status and Progress
Sarah K. Phillips
The University of New Hampshire
May 28, 2013
UNH DOE Review

2. Silicon Microstrip Detectors
Silicon microstrip detectors are used to detect particles that pass through them and are used in
Particle physics experiments at accelerators
Instruments on satellites
Have good properties for particle physics:
Excellent spatial resolution
Good energy resolution
Can cope with high rates
Compact
Are often used in tracking applications!

3. CLAS12 and the JLab Upgrade
Jefferson Lab shut down in May 2012 to do a major upgrade.
The accelerator will be upgraded to 12 GeV (from 6 GeV)
A new experimental hall (Hall D) will be built
The other three experimental halls will also receive beam energies up to 11 GeV
To take advantage of the new energy range, Hall B will upgrade to a new detector system called CLAS12.
Among the new detector systems being developed is a silicon vertex tracker (SVT)
Close to the target; will provide excellent position resolution for vertex determination in reactions.
The UNH Nuclear Group is part of the development of these detectors.

4. CLAS12 and the Jefferson Lab Upgrade

5. CLAS12 and the Jefferson Lab Upgrade

6. Silicon Vertex Tracker
Silicon strips in alternating layers are placed at different angles to provide stereo readout
Layers provide three spatial points for a particle track, allowing for momentum determination by measuring the curvature of the track in the magnetic field of the solenoid.
Barrel-like layers around the target
φ-coverage ~2π
θ-coverage ~ 35° - 125°
Momentum resolution ~50 MeV/c
φ-resolution ~5 mrad
θ-resolution ~20 mrad
Tracking Efficiency > 90%

7. Silicon Vertex Tracker
Each detector is made of:
Three sensors
Front-end electronics
Support structure
Our detectors are being assembled at Fermilab.

8. Silicon Vertex Tracker
Sensors: single-sided, 320 µm silicon
Cross-sectional view showing the different layers of the spacing of the strip
Strip width ~ 8 μm and implant depth 1.3 μm
Readout pitch ~150 μm provides a spatial resolution of ~ 50 μm in r and Φ
Hamamatsu Corporation is making our silicon strip sensors (have experience with CMS and ATLAS)

9. Laser Testing of Silicon Detectors
It is important to perform quality assurance tests and evaluate the performance of the detectors before their installation in the full detector system for CLAS12!
Need to know:
Quality control of the individual detector assemblies
Verify that the fundamental detector properties of the intended design are met.
Laser beams are used to test silicon detectors, since the laser light simulates the signals generated by charged particles in a silicon detector

10. Laser Testing of Silicon Detectors
Concept:
A precision position mechanism scans infrared laser light across the detector.
The data are read out and analyzed for properties such as basic quality assurance, strip-to-strip variations, attenuation along the detector, charge sharing among adjacent readout strips, position resolution, timing resolution, high voltage scans, etc.
The UNH laser testing facility is based on designs used for experiments at Fermilab, Brookhaven, and CERN. For example:
Y. Tomita, M. Nakamura, and K. Niwa, Nucl. Instrum. Meth. A 270, 403 (1988)
S. Shaheen et al., Nucl. Instrum. Meth. A 352, 573 (1995)
T. Akimoto et al., Nucl. Instrum. Meth. A 556, 459 (2006)

11. Laser Testing Facility Design
Fiber Optic Cable
Dark Box/Laser Enclosure
Power Supply
DAQ and Rail Control Computer
Optics
Precision Rails
Detector
Lower-Precision Rail

12. Major Equipment for Facility
Silicon microstrip detectors require careful handling and clean, dry storage.
Cleanroom
Dry storage system
Dark box / laser enclosure
Laser and optics
Precision rail system for scanning
DAQ system

13. Cleanroom Silicon detectors are delicate!
Susceptible to dust and humidity
Require a cleanroom environment
Have special dry storage requirements
Made by Pacific Environmental Technologies, Inc.
Softwall clean room, ISO 7/Class 10,000
12' W x 14' L with an internal 4'x8' gowning room

14. Building the Cleanroom

15. Major Equipment Dry Storage System Dry nitrogen purge system
19.7 cu. ft. chest freezer by GE (inner dimensions: ” w x 23.5” d x 26.22” h)
Teflon 1/4” tubing, single stage brass regulator, compression fittings
Viton o-rings, Dow Corning 739 sealant to seal fittings; PTFE pipe sealing tape to seal the threading.
Flow: plan to run at about 0.48 cubic ft. per hour once we are in production mode; have a max flow rate of 2 cubic ft. per hour.

16. Major Equipment Dark Enclosure DAQ System
Bosch-Rexroth extruded aluminum and aluminum sheeting panels (1/16th thickness); door made from 39” x 39” x 1/8” aluminum plate attached with a piano hinge.
Internal dimensions: 2 m x 1 m x 1 m (outer dimensions about 80 mm larger to account for width of the frame)
Black Poron foam in aluminum angle to ensure light-tightness.
DAQ System
Dell Workstation 9200
C++ code written by UNH students and JLab staff
Data analysis done using ROOT

17. Major Equipment Laser System Optics
Berkeley Nucleonics Corporation Model 106C 2mW
Max power: 1 mW
Spectral peak: 1064 nm, Spectral width: 5 nm
Transition times (10% to 90%): 1 ns rise time, 2 ns fall time
dynamic range: 13 dB
pulse width: internal 3 ns to 640 s
FC connectors
Optics
New Focusing package by OZ Optics (should be able to achieve ~10 m laser spot size).

18. Major Equipment Rail system
Two sections, made by Newmark Systems, Inc.
Precision rails to scan light precisely over sensor
A coarse rail the detector rides on to move to the next sensor in the stave.
Precision rails: three axis
length: x=200 mm, y=200 mm, z=50 mm
resolution: 0.1 m
accuracy: 5 m
repeatability:  0.5 m
max speed = 50 mm/sec
Coarse rail: one rail
16 in. travel
resolution: 0.13 microns
accuracy: mm/mm

19. Laser Test Stand
Precision rail system inside laser enclosure (mounted on optics table)

20. First Measurements
We have been developing our measurements using a surplus CMS detector from Fermilab (pitch 73 μm).
Measurements:
Noise measurements
Gain measurements
Position scans of the strips
Charge sharing between the strips

21. Noise Measurements Procedure:
Inject a known signal from the waveform generator into specific channels
Increase minimum threshold until signal falls to zero
Fit with Gaussian and extract equivalent noise charge (ENC)

22. Gain Measurements Procedure:
Inject a known signals at varying amplitudes from the waveform generator into specific channels
Fit data with linear fit and extract gain from the slope

23. Charge Sharing Measurements
The charge shared across adjacent strips can be described by the function:
η 𝑥 0 = 𝑃𝐻 𝑅 𝑥 0 𝑃𝐻 𝐿 𝑥 0 + 𝑃𝐻 𝑅 𝑥 0
PH denotes the pulse height across the left and right strips.

24. Future Plans All major equipment going
Working on focusing techniques to achieve optimal laser beam spot with the new focusing package
Continue developing the charge sharing measurements and refining measurements to be more automated
Calibration measurements planned with a radioactive source
Test the first article detectors for JLab in fall 2013 – winter 2014
Test the production detectors for JLab (winer 2014 – spring 2014)

25. Conclusions
Lasers are a powerful tool in testing silicon detectors for nuclear and high-energy particle physics experiments.
The laser testing facility at UNH will test the silicon detectors for JLab's CLAS12.
Can be used with silicon sensors for other projects, so will have an extended career.
Great project for undergraduates to get hands-on research experience and make connections at a national lab.

26. Backup Slides

27. Silicon Vertex Tracker
Sensors: single-sided, 320 µm silicon
Cross-sectional view showing the different layers of the spacing of the strip
Strip width ~ 8 μm and implant depth 1.3 μm
Readout pitch ~150 μm provides a spatial resolution of ~ 50 μm in r and Φ
Hamamatsu Corporation is making our silicon strip sensors (have experience with CMS and ATLAS)