The Argonne 6cm MCP-PMT System. Bob Wagner for Argonne LAPPD Collaboration ANNIE Collaboration Meeting Monday 27 Oct 2014

Transcription

1 The Argonne 6cm MCP-PMT System Bob Wagner for Argonne LAPPD Collaboration ANNIE Collaboration Meeting Monday 27 Oct 2014

2 Thanks to Argonne Postdocs Junqi Xie (photocathode) & Jingbo Wang (analysis) for slides and data shown today Dean Walters, Allen Zhao, and Lei Xia (all Argonne) for work on commissioning and operating 6cm Single Tile Processing System Henry Frisch and Matt Wetstein for use of Tektronix oscilloscope for data acquisition Bernhard Adams (Argonne APS) for photodiodes and Rohde & Schwarz oscilloscope. Matt & Bernhard also helped us with navigation of a scope that s smarter than we are 2

3 Small Single Tile Processing System (SmSTPS) R&D Vacuum Transfer System Fabricate 6cm x 6cm active area MCP photodetectors Merger of existing 2-chamber photocathode fabrication & characterization system with indium thermopressure seal development chamber Credit for idea of SmSTPS is due to Dean Walters, Project Engineer Installation & modification began September,

4 Small STPS Chambers Connection to Sealing Chamber Loadlock Bake & Scrub Deposition Sealing 4

5 6cm Active Area MCP Photodetector Composition MCP & Resistive Grid Spacer Stack Getter Strips Stack in Glass Lower Tile Assembly Completed Tube with Photocathode 5

6 Brief History of Small STPS at Argonne October, 2011: Preliminary design for 20cm tile processing system March 6, 2012: Review of Single Tile Facility Suggested Mitigation for Budget and Schedule Risk: Anything that can be done to prove out on a small scale before moving to large scale should be done. In particular, it is recommended that a complete photodetector with all components living together in a system is extremely important. Producing a small scale system and measuring the lifetime of the photodetector sooner rather than later in the program as it is not MCP that limits the lifetime, but the photocathode. March, 2012: Dean Walters suggests using existing photocathode deposition and characterization chambers coupled to LAPPD seal development chamber to make a small form factor tile processing system September, 2012: First two chambers move to Bldg 360 Lab November, 2012: Begin modifications to Deposition Chamber February, 2013: Sealing Chamber and hydraulics moved to Bldg 360 Lab July, 2013: Modified Sealing Chamber arrives in Bldg 360 Lab April, 2014: Initial sealing tests in Sealing Chamber May, 2014: First sealed tubes producing signals: Al photocathodes July 30, 2014: First signal from bialkali photocathode tube September 17, 2014: First long-lived bialkali tube 6

7 Technical Issues Addressed to Achieve Working Tubes Improve Quantum Efficiency of Photocathode High temperature bake capability Reduce Deposition Chamber base pressure Optimize effusion cell evaporation parameters Improve Sealing Yield Dedicated sealing tests in June/July Tune sealing technique parameters, fixturing modifications Increase Tube Lifetime Installation and activation of non-evaporative getters in tubes High temperature bake-out of tube components before sealing Reduce Sealing Chamber base pressure Readout Ready Tubes for Users Mount tubes on readout board. SHV and SMA standard connectors Mitigate potential single point failures 7

8 Results After Addressing May Technical Issues Serial # Date Sealed July 29 Aug 6 Aug 7 Aug 17 Aug 31 Sep 6 Sep 10 Sep 16 Sep 22 Sep 26 Oct 1 Oct 7 Oct 14 Seal Good Good Good/ Cracked Cracked Good Good Cracked Good Good corner leaks Good Good Good MCP Gen I Gen I (none) --- Gen I (bad) Gen I (bad) (none) Gen I Gen II (none) Gen II Gen I Gen II mix Getter Bad Bad Better --- Good Good --- Good Good??? Bad Bad Good Gen II lifetime 1-2 days 1-2 days 4 days (cracked) --- Since 9/1/14 Since 9/8/ Since 9/17/14 Since 9/24/ day 1 day Since 10/15 Tubes were for sealing yield study Tubes 5, 8, 12, 13 were attempts for working tubes. 12 produced first signal. Tubes 22, 26, 29 were photocathode only tubes for QE study Bake-out & Getter activation technique improvement starting with Tube 27 8

9 Bialkali Photocathode for LAPPD small Photodetector Photocathode only tile Evaluate photocathode grown via effusion cells Calibrate in-situ QE monitoring system Current 12 Current / na 1.2 QE % Voltage / V Wavelength /nm 9

10 Phototubes Used in Characterization Studies Quantacon and Planacon MCP-PMT serve as known performance references Testing performed with Hamamatsu diode laser using 405nm head Read-out mainly thanks to UChicago 40 GS/s Tektronix oscilloscope Burle Planacon Burle Quantacon Tube27 Tube28 Tube32 10

11 Analysis approach 1. Record digitized waveforms 2. Fast Fourier Transformation (FFT) 3. Low pass frequency filter 4. Constant Fraction Discriminator (CFD) 5. Obtain timing form Spline Fit 6. Time-Amplitude slewing correction (1) Raw MCP waveform (2) (3) (4), (5) Frequency spectrum Filtered MCP waveform CFD fitting Cutoff frequency Timing Timing 11

12 Timing Performance for Tube 32 (Best Tube) Jitter of reference photodiode ~ 2ps Laser pulse width 70ps FWHM Adds to resolution at low intensity such as single pe study Absolute => jitter referenced to photodiode Differential => resolution for time arrival diff. at opposite ends of single strip line Absolute time resolution Differential time resolution Measured at high light intensity σ = 16.3 ps σ = 6.8 ps 12

13 Signal transmission speed and position resolution (Tube28) X-position scan along strip2 Signal transmission speed: mm/ps The overall distribution is a convolution of beam profile and the detector position resolution: position resolution < 0.5 mm In order to precisely measure the position resolution, we need high precision beam at m level 2 σ = 0.48 mm 13

14 Tube Lifetime Monitoring Working to improve lifetime of tube Lifetime = ability of tube to hold voltage and produce consistent signal Dependent on maintaining UHV in tube vacuum package Tubes are tested and removed Plans for sustained test with laser pulsed on single location Tube27: 34 days Tube28: 27 days Tube32: 6 days 14

15 Single Photoelectron Detection (Tube 28) Limitations of the test Laser Pulse duration: ps (σ = ps, σ = ). Photo emission time cannot be measured within the pulse duration time. Laser beam spot: 1-2 mm, laser has to be focused to m level for differential time resolution measurement Amplitude distribution Charge distribution Gain distribution Npe Mean RMS 1 Gen-II MCP gain = 3.6e7 13 Single pe time resolution is ~ 95ps. Includes laser jitter of 30-40ps 15

16 Rate Scan for Tube 27 16

17 Summary We have made great progress on fabricating 6cm MCP photodetectors since May, 2014 DOE Review Yield increased Lifetime improved for photocathode & overall tube Gain increased Have an established production scheme Maintenance period beginning today will put system in final configuration Having solved most issues for successful fabrication, we are preparing to address issues for improving detector performance We are making plans for distributing tubes to first users Jingbo Wang is delivering Tube 28 to JLab today for studies on EIC RICH detector - Rate - Magnetic Field - Neutron irradiation We are interested in getting tube(s) to ANNIE in early CY2015 (or before?) 17

18 BACK-UP SLIDES 18

19 Laser Wavelength: 405 nm Pulse duration: ~70 ps Pulse frequency: 2 Hz 10 MHz Beam size: 1-2 mm Start time: Photodiode (<2 ps) Readout: oscilloscope, 40 Gs/s (10 Gs/s per channel) Slow controls: Motor driver in x and y directions Micro-meter level precision 40 Gs/s Techtronic scope 405 nm ND filter Splitter ND filter Splitter Pulsed laser diode Test Tube Trigger photodiode mirror Planacon 5 19

20 HV scan (Tube27, Tube28, Tube32) The purpose is to find optimized working HV Tube27 is made of Gen-I MCPs Tube28 is made of Gen-II MCPs, resistance well matched Tube32 is made of Gen-II MCPs, resistance is not well matched. As compared to Tube28, Tube32 has a higher QE but a lower gain. Absolute time resolution Differential time resolution Gen I MCPs Gen I MCPs 16 ps 6 ps 20