Purpose

Proton computed tomography (pCT) will enable accurate prediction of proton and ion range in a patient while providing the benefit of lower radiation exposure than in x-ray CT. The accuracy of the range prediction is essential for treatment planning in proton or ion therapy and depends upon the detector used to evaluate the water-equivalent path length (WEPL) of a proton passing through the object. A novel approach is presented for an inexpensive WEPL detector for pCT and proton radiography.

Methods

A novel multistage detector with an aperture of 10 × 37.5 cm was designed to optimize the accuracy of the WEPL measurements while simplifying detector construction and the performance requirements of its components. The design of the five-stage detector was optimized through simulations based on the geant4 detector simulation toolkit, and the fabricated prototype was calibrated in water-equivalent millimeters with 200 MeV protons in the research beam line of the clinical proton synchrotron at Loma Linda University Medical Center. A special polystyrene step phantom was designed and built to speed up and simplify the calibration procedure. The calibrated five-stage detector was tested in the 200 MeV proton beam as part of the pCT head scanner, using a water phantom and polystyrene slabs to verify the WEPL reconstruction accuracy.

Results

The beam-test results demonstrated excellent performance of the new detector, in good agreement with the simulation results. The WEPL measurement accuracy is about 3.0 mm per proton in the 0-260 mm WEPL range required for a pCT head scan with a 200 MeV proton beam.

Conclusions

The new multistage design approach to WEPL measurements for proton CT and radiography has been prototyped and tested. The test results show that the design is competitive with much more expensive calorimeter and range-counter designs.

The central drift chamber for the BaBar detector at the SLAC B-factory is based on a hexagonal cell design with 7104 cells arranged in 40 layers and drift gas Helium:isobutane (80%:20%). Performance optimization and integration requirements led to an electronics design that mounts the amplifier-discriminator and digitizing circuitry directly on the endplate. High channel density is achieved using a 4-channel custom amplifier-discriminator IC and an 8-channel custom CMOS TDC/FADC IC on a single circuit board. Data read from the front ends are multiplexed on 4 fiber optic links, and prompt trigger data are sent out continuously on 24 links. Analysis of cosmic ray data demonstrates that the electronics design meets the performance goals for the BaBar drift chamber. The final electronics were installed on the drift chamber in July, 1998. Installation of BaBar on beamline is scheduled for March, 1999. © 1999 IEEE.

These reports present the results of the 2013 Community Summer Study of the APS Division of Particles and Fields ("Snowmass 2013") on the future program of particle physics in the U.S. Chapter 8, on the Instrumentation Frontier, discusses the instrumentation needs of future experiments in the Energy, Intensity, and Cosmic Frontiers, promising new technologies for particle physics research, and issues of gathering resources for long-term research in this area.

We have observed the decays B--> phiK and phiK(*) in a sample of over 45 million B mesons collected with the BABAR detector at the PEP-II collider. The measured branching fractions are B(B+--> phiK+) = (7.7(+1.6)(-1.4)+/-0.8)x10(-6), B(B0--> phiK0) = (8.1(+3.1)(-2.5)+/-0.8)x10(-6), B(B+--> phiK(*+)) = (9.7(+4.2)(-3.4)+/-1.7)x10(-6), and B(B0--> phiK(*0)) = (8.7(+2.5)(-2.1)+/-1.1)x10(-6). We also report the upper limit B(B+--> phipi(+))<1.4x10(-6) ( 90% C.L.).

We search for direct CP violation in charmless hadronic B decays observed in a sample of about 22.7 million B B̄ pairs collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e+e- collider. We measure the following charge asymmetries: ACp(B ±→η′K±=-0.11±0. 11±0.02, ACP(B±→ωπ ±) = -0.01 -0.31+0.29±0.03, ACPB±→φK±)= -0.05±0.20±0.03, ACP(B± → φK*±)= -0.430.30+0.36±0.06, and ACP(B0→φ K*0)=0.00±0.27±0.03. © 2002 The American Physical Society.

The production of J/psi mesons in continuum e(+)e(-) annihilations has been studied with the BABAR detector at energies near the Upsilon(4S) resonance. The mesons are distinguished from J/psi production in B decays through their center-of-mass momentum and energy. We measure the cross section e(+)e(-)-->J/psi X to be 2.52+/-0.21+/-0.21 pb. We set a 90% C.L. upper limit on the branching fraction for direct Upsilon(4S)-->J/psi X decays at 4.7 x 10(-4).