Development of an external PIGE method using nitrogen from atmospheric air as external beam current normalizer and its application to nondestructive quantification of total boron mass fraction in boron containing neutron absorbers.

Beam current monitoring and normalization is a very important task in ion beam analysis experiments. Compared to current monitoring by conventional method, in situ or external beam current normalization is attractive in Particle Induced Gamma-ray Emission (PIGE), which involves simultaneous measurement of prompt gamma rays of analyte of interest and current normalizing element. In the present work, an external (in air) PIGE method has been standardized for quantification of low Z elements using nitrogen from atmospheric air as external current normalizer, in which 2313 keV of 14N(p,p'γ)14N is measured. It provides truly nondestructive and greener quantification method for low Z elements by external PIGE. The method was standardized by quantifying total boron mass fractions in ceramic/refractory boron-based samples using low energy proton beam from tandem accelerator. The samples were irradiated with 3.75 MeV proton beam and prompt gamma rays of analyte at 429, 718 and 2125 keV of 10B(p,αγ)7Be, 10B(p,p'γ)10B and 11B(p,p'γ)11B, respectively, and external current normalizers at 136 and 2313 keV were measured simultaneously using high resolution HPGe detector system. The obtained results were compared with external PIGE method using tantalum as external current normalizer, where 136 keV of 181Ta(p,p'γ)181Ta from beam exit window material (Ta) was used for current normalization. The developed method is found to be simple, rapid, convenient, reproducible, truly nondestructive and more economical as no additional beam monitoring instruments are required and it is especially advantageous for direct quantitative analysis of 'as received' samples.

Beamline characterization of a dielectric-filled reentrant cavity resonator as beam current monitor for a medical cyclotron facility.

At PSI (Paul Scherrer Institute), Switzerland, a superconducting cyclotron called "COMET" delivers proton beam of 250 MeV pulsed at 72.85 MHz for proton radiation therapy. Measuring proton beam currents (0.1-10nA) is of crucial importance for the treatment safety and is usually performed with invasive monitors such as ionisation chambers (ICs) which degrade the beam quality. A new non-invasive beam current monitor working on the principle of electromagnetic resonance is built to replace ICs in order to preserve the beam quality delivered. The fundamental resonance frequency of the resonator is tuned to 145.7 MHz, which is the second harmonic of the pulse rate, so it provides signals proportional to beam current. The cavity resonator installed in the beamline of the COMET is designed to measure beam currents for the energy range 238-70 MeV. Good agreement is reached between expected and measured resonator response over the energy range of interest. The resonator can deliver beam current information down to 0.15 nA for a measurement integration time of 1 s. The cavity resonator might be applied serving as a safety monitor to trigger interlocks within the existing domain of proton radiation therapy. Low beam currents limit the abilities to detect sufficiently, however, with the potential implementation of FLASH proton therapy, the application of cavity resonator as an online beam-monitoring device is feasible.