High-energy photon beam production with laser-Compton backscattering

We have produced a beam of high-energy gamma-rays by Compton backscattering of $\text{1064}\text{nm}$ laser photons from 1 GeV electrons circulating in a storage ring. Measuring the energy spectra of the backscattering photons with an HPGe detector, we have found that the maximum energy of $\text{17.6}\text{MeV}$ and the measured energy spectra show agreement with the simulation calculations, while the detected photon yields were measured at about 4×10³, 2×10³ and $\text{3×10}{}^2\text{photons}\text{s}{}^{\mathrm{-1}}\text{mA}{}^{\mathrm{-1}}\text{W}{}^{\mathrm{-1}}$ for the 20, 10 and $\text{2}\text{mm}\text{φ}$ collimators, respectively. The photon energy widths from the collimators correspond to 6.6–$\text{17.6}\text{MeV}$, 12.4–$\text{17.6}\text{MeV}$ and 17.3–$\text{17.6}\text{MeV}$, respectively. By using these photons, we measured the total nuclear photoabsorption cross-sections in the E1 giant resonance energy region for ${}^{197}\text{Au}$ using the attenuation method and we have demonstrated that the photon attenuation method will be a useful tool for studying photonuclear reactions.     

A compact planar positron imaging system

A planar imaging system for positron-emitting radiotracers was developed and its physical performance was evaluated. The new device consists of two opposing planar detectors, each having 4 (columns) $\text{×}\text{6}$ (rows) detector units, and each unit composed of 10×10 arrays of $\text{2×2×20}\text{mm}{}^3$ pillars of Bi₄Ge₃O₁₂ (BGO) scintillators and a metal-packaged position-sensitive photomultiplier tube. The system is very compact and has a simple structure that allows versatile positioning of detectors in the horizontal or vertical mode. Focal plane images are constructed from coincidence data collected by opposing planar detectors. The system provides good quality images even in a short period of time or with low tracer activity. Spatial resolutions of 1.6–$\text{2.1}\text{mm}$ FWHM were achieved for the entire field of view. The sensitivity was $\text{107}\text{cps}\text{/}\text{kBq}\text{/}\text{ml}$ measured in a uniform flat phantom. In this study, the capability of the new system was demonstrated by the imaging of radiotracer distribution in rats and plants.     

A high resolution,low background fast neutron spectrometer

We discuss the possibility to create a spectrometer of full absorption based on liquid scintillator doped with enriched ${}^6$Li. Of specific interest, the spectrometer will have energy resolution estimated to lie in the range 5–10% for 14 MeV neutrons. It will be sensitive to fluxes from 10⁻⁴ to $\text{10}{}^6\text{cm}{}^{\mathrm{-2}}\text{s}{}^{\mathrm{-1}}$ above a threshold of 1 MeV in a γ-background of up to $\text{10}{}^4\text{s}{}^{\mathrm{-1}}$. The detector's efficiency will be determined by the volume of the scintillator only (∼3 l) and is estimated to be 0.2–10%. The main reason for the poor resolution of an organic scintillator based spectrometer of full absorption is a non-linear light-yield of the scintillator for recoil protons. The neutron energy is occasionally distributed among recoil protons, and due to non-linear light-yield the total amount of light from all recoil protons ambiguously determines the initial neutron energy. The high-energy resolution will be achieved by compensation of the non-linear light-yield of the scintillator through the use of optically separated sections. The applications of such a detector for low-background experiments in fundamental physics research, characterizations of neutron fluence in space, and the health physics community are discussed.     

Data acquisition and monitoring for the KLOE detector

The Data Acquisition system for the KLOE experiment, presently running at the Laboratori Nazionali di Frascati DAΦNE collider, has been designed to sustain an acquisition throughput of $\text{50}\text{Mbyte}\text{/}\text{s}$ for an event rate of $\text{10}\text{kHz}$. Its two major components are the front end data readout, based on custom buses, and a complex network of computers and storage devices hosting a set of distributed processes. The end result is a seamless data transport from the readout system to the storage library, accompanied by concurrent on line calibrations and data quality control.     

Improved surface treatment of the superconducting TESLA cavities

The proposed linear electron–positron collider TESLA is based on $\text{1.3}\text{GHz}$ superconducting niobium cavities for particle acceleration. For a centre-of-mass energy of $\text{500}\text{GeV}$, an accelerating field of $\text{23.4}\text{MV/m}$ is required which is reliably achieved with a niobium surface preparation by chemical etching. An upgrade of the collider to $\text{800}\text{GeV}$ requires an improved cavity preparation technique. In this paper, results are presented on single-cell cavities which demonstrate that fields of up to $\text{40}\text{MV/m}$ are accessible by electrolytic polishing of the inner surface of the cavity.     

Calibration of a neutron time-of-flight multidetector system for an intensity interferometry experiment

We present the details of an experiment on light particle interferometry. In particular, we focus on a time-of-flight technique which uses a cyclotron RF signal as a start and a liquid scintillator time signal as a stop, to measure neutron energy in the range of E_n≈1.8–$\text{150}\text{MeV}$. This dynamic range (up to $\text{300}\text{ns}$) is much larger than the beam bunch separation $\text{(54}\text{ns}\text{)}$ of the AGOR cyclotron (KVI). However, the problem of a short burst period is overcome by using the time information obtained from a fast projectile fragment phoswich detector. The complete analysis procedure to extract the final neutron kinetic energy spectra, is discussed.