Detector R&D in Group EB

Image of BABAR Detector, Photo taken by Peter Ginter, SLAC 2002

Research Goal

Group B is involved in the R&D toward novel Particle Identification (PID) detectors at future experiments, such as the proposed SuperB Factory in Italy. One such idea is a Fast Focusing DIRC (fDIRC), which is derived from the BABAR DIRC system by improving the precision of the time measurement and by making it less sensitive to accelerator induced background that is expected to limit the DIRC particle identification performance if the luminosity at the B-Factory (or a Super B-Factory) increases to or beyond 1035cm-2sec-1. The approach is to modify the current photon detection method by eliminating the water filled standoff region that is the main source of background in the DIRC and by replacing the conventional photomultiplier tubes (PMTs) currently used with new photo detectors that provide superior timing. The fast timing will allow, for the first time in a RICH detector, the correction of the chromatic error during Cherenkov photon production.

Photodetector Tests

The DIRC uses an array of about 11,000 densely packed conventional photomultiplier tubes for photo-detection. These PMTs (ETL model 9125) have high gain and good quantum efficiency (around 25%) in the Cherenkov wavelengths transmitted by both quartz and water, and are available at modest price. The transit time resolution is about 1.5nsec.

New single photon detectors are now available that provide significantly better time resolution, 100ps or better, while maintaining a comparable gain and quantum efficiency. These devices include hybrid photodiodes (HPDs), microchannel plate (MCP) PMTs and flat panel two-dimensional PMTs. Since those are still very new, it is interesting and important to measure the response and uniformity of such devices and compare them to the ETL9125 PMT. We have developed a setup that uses a motion controlled multi-axis stage to scan a picosecond laser across the surface of the new photon detector. The detectors are read-out by CAMAC crate electronics. The data acquisition software has been developed within our group.

Tests currently focus on the Hamamatsu H8500 PMT (64 channel Flat Panel two-dimensional multi-anode PMT) and the Burle 85011 MCP (64 channel multi-anode microchannel plate PMT).

Cosmic Ray Telescope (CRT)

Replacing the water-filled standoff region requires a new design for the Cherenkov ring expansion region. Efforts have started to use detailed detector simulation to optimize the new optics and placement of the new photon detectors. To facilitate a full-scale test of a prototype of the new optics, a cosmic ray telescope (CRT) facility has been constructed.

The CRT consists of two scintillator panels providing the primary trigger, a scintillation counter hodoscope with ~3mm spacial and ~1mrad angular resolution and an iron stack with four layers of iron plus scintillator panels. The stack provides momentum bins of ~400MeV/c with a cutoff at ~2GeV/c. The PMTs of the CRT are read-out by CAMAC and NIM crate electronics. The data acquisition has been developed within our group.

Currently, the CRT performance is being studied and track reconstruction software is being developed.

Cherenkov time-of-flight detector

Using a small radiator made of synthetic fused silica, very fast electronics, and MCP-PMTs we have constructed a prototype of a high-resolution time-of-flight (TOF) detector based on Cherenkov light. Using pulsed laser diodes we were able to achive a timing resolution of 7.2ps for events with 50 photoelectrons. This detector is capable of excellent pion/kaon separation, similar to the DIRC system. However, while the DIRC system in its current design is limited to PID in the detector barrel, this TOF detector could be placed as an endcap PID system in future experiments.

Prototype in a Hadronic Particle Test Beam

A prototype of the Focusing DIRC, consisting of a single DIRC radiator bar, a stand-off region filled with mineral oil, a focusing mirror, and an array of multi-anode PMTs, has been installed in Endstation A at SLAC.
The setup also includes a prototype of the new TOF detector.

During the summer of 2005, 2006, and 2007 data was taken in a particle test beam, further time in a test beam is expected for 2008. Calibration of the readout electronics, developed at SLAC, is close to completion and the data analysis software is being optimized. First results were presented at recent conferences.

Research Team

The research team currently consists of:
Jose Benitez, Dr. Clive R. Field, Prof. David W.G.S. Leith, Matt McCulloch, Dr. Blair N. Ratcliff, Dr. Jochen Schwiening, and Dr. Jaroslav Va'vra.

Graduate Student Contact

In addition to learning and eventually running the BABAR detector and, doing physics analysis with BABAR data, the DIRC R&D research provides many interesting hardware research topics for Stanford physics graduate students.

We currently offer research opportunities for new Stanford physics graduate students to join in our work under the supervision of Prof. Leith and Dr. Ratcliff.
Some of the topics include:

Please refer to the group B research opportunities page for details on those and other research opportunities available in group B.


Presentations at International Conferences:

Relevant Links: