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The UC Simulation of Picosecond Detectors
Pico-Sec Timing Hardware Workshop
November 18, 2005
Timothy Credo
TOF Detection Current method: bars of
scintillator several meters long
Signal amplified in PMT at each end
Relevant length scale is 1 in, which governs time resolution (100 ps)
1 picosecond resolution requires scale on the order of 300 microns
A Picosecond TOF Detector
Light produced in the window of MCP-PMT shines on a photocathode
Signal amplified in MCP, and summed in the anode
Electronics measure pulse from four collection points
Summing Multianode
Multilayer circuit board collects MCP signal
16x16 125 micron pads each routed to electronics by equal-time impedance-matched traces
4 central collection points deliver signal to electronics
Mismatched impedances cause signal reflections
Simulations (Window, MCP)
Cherenkov emission, transmission, chromatic dispersion, and quantum efficiency simulated in ROOT (started by R. Schroll)
Simulations use MCP time spread and gain (1e6) for single photons to estimate the signal arriving on the anode
These data were input into an HSPICE simulation of the summing anode
Window Thickness and Material Simulations evaluated the
time resolution of the window and MCP for different window materials and thicknesses
MgF2 is transparent further into the ultraviolet and offers better performance
Larger windows generate more photons, providing a better average over TTS
Window Width (mm)
RMS Jitter (picoseconds)
Number of Photoelectrons
Silica MgF2 Silica MgF2
1.0 15.31 12.88 16.3 21.6
2.0 10.21 8.74 32.4 42.6
3.0 8.39 7.22 48.2 63.0
4.0 7.12 6.06 63.6 83.2
5.0 6.80 5.71 78.2 102.6
6.0 6.34 5.18 93.0 122.0
7.0 5.71 4.85 109.0 141.0
8.0 5.29 4.59 121.9 159.4
Time Resolution (Window, MCP) The time resolution of the
window and MCP depend on the number of photons detected and on the TTS of the MCP
With the Burle Planacon MCP, simulations indicate a 6 picosecond resolution
A smaller TTS (already achieved in smaller area MCPs) would make 1 ps resolution possible
Average timing of signals arriving at the anode, for different MCPs
Simulations (Anode) The performance of the
multianode was simulated in HSPICE using a spice model generated from the board design using HyperLynx
With a 50 Ω termination, ringing decayed with a time constant of τ = 5.5 ns
With 60 ps TTS, pulse had average rise time of 80 ps, and average height .25 V
With 10 ps TTS, average rise time was 25 ps, and average height 1.2 V Voltage vs. time plots of anode
simulations, with 60 ps TTS (top) and 10 ps TTS (bottom)
Ten Simulated Pulses (60 picosecond TTS)
Ten Simulated Pulses (10 picosecond TTS)
Time Resolution (Anode)
With a large TTS (σ = 60 ps), the pulse shape is not consistent
With this anode a resolution of around 10 to 20 picoseconds could be achieved for a large TTS
With a faster MCP, the pulse shape is more stable
Picosecond resolution may be possible, but not without a fast large area MCP (TTS comparable to smaller area MCPs)
Future Plans Custom summing board
mates with standard 32x32 Burle anode
Glue boards to Burle PMT with Planacon MCP using conductive epoxy (Greg Sellberg, Fermilab)
Solder component board with fast comparators
Use commercial TDC(?) and test several tubes in a beam at Fermilab or Argonne
Conclusion and Questions A picosecond TOF detector could be
developed, but would rely on a fast large area MCP and fast electronics
Is the MCP response to a single photoelectron a good approx. to its behavior in the case of many photoelectrons?
Will the particle create a pulse as it passes through the anode and the electronics, and what effect will this have?