Masayo Suzuki

Studies of light emission by continuously sensitive avalanche chambers

Abstract The optimal conditions for the optical recording of images of electron avalanches between parallel meshes have been studied. The emission spectra of gas mixtures have been investigated, where triethylamine (TEA), tetrakis(dimethylamine)ethylene (TMAE), and nitrogen, are used as the photon-emitting agents. For a given charge gain, the photon intensity decreases with electric field. This favours amplification between parallel meshes instead of wires. The use of intensified CCD cameras permits the recording of the local energy loss along the tracks.

An optical, proportional, continuously operating avalanche chamber

Abstract We describe a simple structure, made of two parallel transparent meshes at a distance of 9 mm from each other, which permits one to observe avalanches generated by radiations with an image intensifier with a moderate Townsend amplification factor of about 4 × 10 4 . The filing gas contains triethylamine, which emits a light spectrum peaked at 280 nm, in proportion of around one photon per ionized atom in the avalanche. Examples of tracks from various radiations, obtained by amplifying the ionization electrons in a drift space filled with the gas or with a high-density grid, show a good recognition capability, even for a complex pattern of trajectories under conditions where the collected charges and emitted light are proportional to the energy lost in the gas, over a rather wide range. The present study could demonstrate the possibilities of applying this chamber to the detection of complex events and the observation of rare ones.

The emission spectra of Ar, Kr and Xe + TEA

Abstract The emission spectra of Ar, Kr and Xe + 6% TEA gas mixtures are measured by using a single wire proportional counter as the emission source. Asymmetric emission bands are observed in the range of 270 to 350 nm, which can be attributed to the radiative deexcitation of excited TEA molecules. For the practical application of optical readout of avalanche chambers, the Ar + 2.0% TEA + 20% isobutane gas mixture is also examined, and nearly the same emission band is observed.

Some applications of the imaging proportional chamber

Photons emitted by avalanches in gases can be detected with an image intensifier coupled to a solid-state camera. Some vapors enhance the emission at wavelengths close to the visible. Progress made in using this technique to image charged particles and Cherenkov photons is described. Results are presented for various gas mixtures containing TEA and TMAE. >

On the optical readout of gas avalanche chambers and its applications

Abstract Gaseous avalanche counters with mixtures containing the vapour of triethylamine, are coupled to an optical readout system. Different configurations are studied in order to visualize ionization tracks produced by high-energy particles or images caused by vacuum ultraviolet light. This instrument has potential applications in the study of rare or complex events - such as the search for double-beta and proton decay - or in Cherenkov ring imaging.

A highly efficient low-pressure UV-rich detector with optical avalanche recording

Abstract UV photons from a Cherenkov radiator are multiplied in a multistep avalanche chamber operating in a gated mode at low gas pressure (40 Torr). The gas mixture is C 2 H 6 -argon ( 80 20 ) and TMAE at 34°C. Visible light emitted from single photoelectron avalanches is detected by a CCD camera coupled to an image intensifier system. The detector was tested with 5 GeV c electrons, using a CH 4 radiator gas at 1 atm. Cherenkov rings essentially free of particle background and of secondary photon feedback were obtained in this mode of operation with a mean number n ≅ 11.5 ( N 0 ≅ 76 cm −1 ). We present this new method and discuss its performance.

A MULTIPLE CCD X-RAY DETECTOR AND ITS FIRST OPERATION WITH SYNCHROTRON RADIATION X-RAY BEAM

A 4×4 array structure of 16 identical CCD X-ray detector modules, called the multiple CCD X-ray detector system (MCCDX), was submitted to its first synchrotron radiation experiment at the protein crystallography station of the RIKEN beamline (BL45XU) at the SPring-8 facility. An X-ray diffraction pattern of cholesterol powder was specifically taken in order to investigate the overall system performance.

A new microdosimetric instrument based on a proportional scintillation imaging chamber for heavy ion track investigation

Abstract The ionization track structures formed by energetic heavy ions in matter are of great importance in radiochemistry, radiobiology, and medical applications. We proposed a proportional scintillation imaging chamber (PSIC) as a new microdosimetric instrument to investigate heavy ion track structures, since it can provide us with high-quality, real-time photographic images of ionization tracks generated by ionization radiation. We have constructed and installed a prototype of PSIC in the E5 beamline of the RIKEN Ring Cyclotron. It has been successfully operated, revealing the details of the ionization track structures ( Core-Penumbra Structure ) of Ar (95 MeV/u) and N (135 MeV/u) ions.

A proportional scintillation X-ray imaging chamber and its performance

Abstract We discuss the operational principle of a proportional scintillation X-ray imaging chamber, and report the performance of the first prototype constructed for SPring-8. Single X-ray photons have been successfully imaged with the prototype as bright spots of 1.4 mm in diameter, as expected. The absolute detection efficiency has been found to be 2.4%, consistent with the predicted value. The fluctuation in the light gain uniformity was less than 7% over the entire detection area. The linearity of response has been examined by measuring the gray value distribution of single X-ray photons detected. The spatial resolutions attained in analogue mode and in digital mode were around 1 mm and better than 170 μm, respectively.

High Flux X‐ray Beam Intensity Monitor Based upon Rare Gas Scintillation

We have developed a new X‐ray beam intensity monitor based upon rare gas scintillation in order to solve (i) the non‐ion‐saturation problem occurring ionization chambers when irradiated with high flux X‐ray beams and (ii) the slow time response of ionization chambers. When argon gas is used, it has been confirmed that the scintillation output was proportional to an X‐ray intensity up to 1015 xph/sec, and responded to an X‐ray beam with a time resolution better than 50 nsec. The rare gas scintillation X‐ray beam monitor developed is compatible to ionization chamber in terms of its readout electronics and the physical size, so that it can easily substitute existing ionization chambers when needed.