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?