ISS, Rome, Italy
ENEA C.R. Frascati, Frascati (Roma), Italy
Azienda Ospedaliera Papardo, Messina, Italy
ENEA-Bologna, Bologna, Italy
University of Rome "La Sapienza", Rome, Italy
A dedicated dose delivery monitor is under development for the TOP-IMPLART proton accelerator, the first LINAC for cancer therapy. It is expected to measure the intensity profile to precisely monitor the fully active 3+1D (x/y/z and intensity) dose delivery of each short pulses (few micro-s, 0.1-10 micro-A pulse current at ~100 Hz) of the therapeutic proton beam (up to 230 MeV). The monitor system consists of planar gas chambers operating in ionization regime with cathode plane made ofμpattern pads alternately connected by orthogonal strips*. The dedicated readout electronics features trans-impedance amplifier that dynamically adapts its integrating feedback capacitance to the incoming amount of charge, then opportunistically changing its gain. The measured absolute sensitivity is about 100 fC (better than 0.03 relative sensitivity), the dynamic range up to 10000 (2 gain settings) with time response at the level of few ns, and virtually no dead time. Small scale chamber prototype (0.875 mm pitch pads) and readout electronics have been tested and characterized under both electron (5 MeV) and proton (up to 27 MeV) beams.
* The pad-like design has been adopted to maximize the field uniformity, to reduce the chamber thickness and to obtain both x/y coordinates on a single chamber.
ENEA C.R. Frascati, Frascati (Roma), Italy
The results of a 27MeV proton LINAC commissioning are presented. The linac, operating at ENEA Frascati Research Center, consists of a 425MHz injector followed by a 3GHz booster. The injector is a commercial LINAC (ACCSYS-HITACHI PL7) composed by a duoplasmatron source with einzel lens, a 3MeV RFQ and a 7MeV DTL. Wide injection current range (0-1.5mA) is obtained varying extraction and lens potentials. The booster is a sequence of 3 SCDTL (Side Coupled DTL) modules with output energies of 11.6, 18 and 27MeV. Each module requires less than 2MW peak power in 4us length pulses. All modules are powered by a single klystron. The output beam has been characterized at 10Hz PRF. Fast AC transformers, Faraday cup and ionization chamber have been used for current/charge monitoring, while energy has been measured using a novel detector based on LiF crystals. Systematic measurements have been done to investigate the sensitivity of output beam to machine operating parameters (SCDTL temperatures, stability of injector and RF power) highlightning the existing correlations. The LINAC is part of a 150MeV protontherapy accelerator under development in the framework of the TOP-IMPLART Project.