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PImMS: Pixel Imaging Mass Spectrometry with Fast Pixel Detectors

PImMS: Pixel Imaging Mass Spectrometry with Fast Pixel Detectors Mark Brouard, Edward Halford, Jason Lee, Craig Slater, Claire Vallance, Edward Wilman, Benjamin Winter, Weihao Yuen Chemistry, University of Oxford Jaya John John, Laura Hill, Andrei Nomerotski

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PImMS: Pixel Imaging Mass Spectrometry with Fast Pixel Detectors

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  1. PImMS: Pixel Imaging Mass Spectrometry with Fast Pixel Detectors Mark Brouard, Edward Halford, Jason Lee, Craig Slater, Claire Vallance, Edward Wilman, Benjamin Winter, Weihao Yuen Chemistry, University of Oxford Jaya John John, Laura Hill, Andrei Nomerotski Physics, University of Oxford Andy Clark, Jamie Crooks, Renato Turchetta Rutherford Appleton Laboratory VERTEX 2011, June 2011

  2. Outline • PImMS: Pixel Imaging Mass Spectrometry • Proof of concept experiments • First results with PImMS1 Sensor

  3. Mass Spectrometry Very popular tool in chemistry, biology, pharmaceutical industry etc. TOF MS: Heavier fragments fly slower Mass spectrum for human plasma Total Time ~ 100 msec • Measure detector current: limited to one dimension • Mass resolution M/dM for TOF MS up to 50000

  4. Ion Imaging • Fix a mass peak • Measure full scattering distribution of fragment ions • Sensitive to fragmentation process S atom ion images for OCS photodissociation at 248nm

  5. Visible light detection pixel sensor MCP Phosphor Electron detection E pixel sensor MCP Visible Light vs Direct Detection Typically use visible light but direct detection of electrons after MCP is possible

  6. Pixel Imaging Mass Spec: PImMS PImMS = Mass Spectroscopy ΧIon Imaging • Recent progress in silicon technologies: fast pixel detectors overcome the single mass peak limitation • Since 2009 a 3-year project funded by STFC in UK to build a fast camera for mass spec applications

  7. Pixel Imaging Mass Spec: PImMS • Imaging of multiple masses in a single acquisition • Mass resolution determined by flight tube, phosphordecay time and camera speed

  8. Fast Framing CCD Camera First proof of principle experiments: CCD camera by DALSA (ZE-40-04K07) 16 sequential images at 64x64 resolution Pixel : 100 x 100 sq.micron Max frame rate 100 MHz (!) Principle: fast, local storage of charge in a CCD register at imaging pixel level Limitation: number of frames DALSA camera

  9. Velocity Mapped PImMS (1) 2007-2008: Proof of concept experiment successfully performed on dimethyldisulfide (DMDS)3 Ionization and fragmentation performed with a polarized laser, data recorded with DALSA camera. CH3S2CH3 3: M. Brouard, E.K. Campbell, A.J. Johnsen, C. Vallance, W.H. Yuen, and A. Nomerotski, Rev. Sci. Instrum.79, 123115, (2008)

  10. Possible applications (1) • Surface imaging for separate mass peaks • Replace scanning with wide-field imaging R.Heeren et al

  11. Possible applications (2) • Parallel processing– high throughput sampling

  12. Possible applications (3) • Fingerprinting of molecules mass fingerprinting of human serum albumin (from Wikipedia)

  13. PImMS Sensor: Imager with time stamping

  14. Fast Framing vs Time Stamping • Time stamping provides same information generating much less data • BUT needs low intensity (one pixel hit only once or less) Time stamping

  15. Spin-off of ILC Sensor R&D PImMS and International Linear Collider have similar data structure PImMS : 0.2 ms duration @ 20 Hz ILC: 1.0 ms duration @ 5 Hz 0.05 s 0.2 ms 337 ns 0.2 s 2820x 0.95 ms PImMS ILC time

  16. Signal detected in thin epitaxial layer < 20 mm Limited functionality as only NMOS transistors are allowed PMOS transistors compete for charge Monolithic Active Pixel Sensors • INMAPS process developed at RAL • Shields n-wells with deep p+ implant • Full CMOS capability PImMS1 sensor

  17. PImMS 1 Specs • 72 by 72 pixel array • 70 um by 70 um pixel • 5 mm x 5 mm active area • 50 ns timing resolution • 12 bit time stamp storage • 4 memories per pixel • 1 ms maximum experimental period • Programmable threshold and trim

  18. Ion Intensity Simulations • Important to be sensitive to heavy fragments • Simulated probability to have N hits/pixel • Four buffers allow higher intensity

  19. The PImMS Pixel Preamplifier Charge Collection Diodes Shaper Comparator

  20. PImMS Pixel

  21. PImMS1 Technology • 615 transistors in every pixel • Over 3 million transistors • Submitted in Aug 2010, received in Nov 2010 • 0.18 um CMOS fabrication • INMAPS process (Rutherford Appleton Lab)

  22. PImMS1 Sensor 7.2 mm

  23. PImMS Camera System

  24. PImMS Camera PImMSTesting

  25. PImMS Camera read out over a USB cable.

  26. First Analogue Image

  27. First Digital Readout Image Two laser pulses separated by 300 ns

  28. PImMS1 Digital Readout Five laser pulses, each at a different time

  29. Digital Readout – 3D interpretation Timecode Pixel position - y Pixel position - x

  30. Pixel Masking Arbitrary masks are possible Three laser pulses separated in time

  31. Sensor Characterization Photon Transfer Curve Poisson distribution of signal  Noise = sqrt(Signal)  absolute calibration Full well capacity 24ke Quantum efficiency: 8-9% for visible light, max @ 470 nm Front illuminated sensor Slope = 0.5

  32. Threshold Trim • Each pixel has a trim register: 4 bits to adjust threshold • Maximum trim ~50mV • Calibration procedure equalizes thresholds for all pixels • Dispersion (sigma) before and after calibration 12.8  3.6 mV (~70 e)

  33. TOF MS in Oxford Chemistry PImMS sensor is mounted here

  34. Comparison of PImMS and PMT • Same mass peaks seen with PImMS as with a photomultiplier tube (PMT) • Two fragments of CHCA • 1.5 kV MCP; 4.0 kV Phosphor screen

  35. One of the two PImMS peaks • PImMS : 50 ns per timecode • FWHM ≈ 100ns in both

  36. Ions Detected vs MCP Voltage # of ions/cycle MCP voltage (kV)

  37. FWHM vs MCP Voltage FWHM (us) 100 ns MCP voltage (kV)

  38. Ion Imaging Modes Velocity mapping Spatial mapping

  39. Spatial Mode Imaging Potential applications: forensics and tissue analysis Ion image Microscope image (Trypan blue)

  40. First PImMS spatial imaging results Conventional CCD camera image oriented 45o to PImMS

  41. Spatial Imaging Spatial map imaging First PImMS spatial imaging results Conventional camera PImMS sensor

  42. Multi-hit Capabilities Spatial map imaging First PImMS spatial imaging results: four registers 1 2 Intensity 3 4 Time of flight

  43. Next Steps: PImMS 2 and beyond • Larger Array 324 x 324 pixels • 23 x 23 sq.mm active area • 50 Frames/second with existing PImMS camera • Max 380 Frames/second • Reduced interface pin count for vacuum operation • Possible future directions Faster: 101 ns Larger: wafer scale sensors More sensitive: backthinned Intensity information: ToT Build-in ADC

  44. Summary Pixel Imaging Mass Spectroscopy is a powerful hybrid of usual TOF MS and Ion Imaging Progress in sensor technologies allows simultaneous capture of images for multiple mass peaks First PImMS sensor under tests since Feb 2011, second generation sensor in the end of 2011 Other applications, ex. atom probe tomography, fluorescent imaging etc

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