[en] The Institute for Nuclear Research and Nuclear Energy is preparing to operate a high-power cyclotron for production of radioisotopes for nuclear medicine, research in radiochemistry, radiobiology, nuclear physics, solid state physics. The cyclotron is a TR24 produced by ASCI, Canada, capable to deliver proton beams in the energy range of 15 to 24 MeV with current as high as 400 µA. Multiple extraction lines can be fed. The primary goal of the project is the production of PET and SPECT isotopes as ¹⁸F, ^67,68Ga, ^99mTc, etc.

This contribution reports the status of the project. Design considerations for the cyclotron vault will be discussed for some of the target radioisotopes. (paper)

[en] The results presented in the current paper are part of the studies which we are conducting in regards with the radiological characterization of the cyclotron facility that is currently being built by the Institute for Nuclear Research and Nuclear Energy at the Bulgarian Academy of Sciences. The facility is going to be dedicated to research and development of radiopharmaceuticals and ¹⁸F is of primary interest. Adding a local shielding around the target will be useful in limiting the spatial distribution of the emitted secondary neutrons(during the target irradiation) and the activation of the bunker walls. The effect of adding a layer of borated polyethylene is studied. We are considering a simplified spherical geometry, divided into spherical shells, of the bunker walls. By employing the FLUKA Monte-Carlo transport code we obtained results for the distribution of the fluence of the secondary neutrons and the activated radionuclides in the spherical shells.

[en] We report results on the performance of a free-electron laser operating at a wavelength of 13.7 nm where unprecedented peak and average powers for a coherent extreme-ultraviolet radiation source have been measured. In the saturation regime, the peak energy approached 170 J for individual pulses, and the average energy per pulse reached 70 J. The pulse duration was in the region of 10 fs, and peak powers of 10 GW were achieved. At a pulse repetition frequency of 700 pulses per second, the average extreme-ultraviolet power reached 20 mW. The output beam also contained a significant contribution from odd harmonics of approximately 0.6% and 0.03% for the 3rd (4.6 nm) and the 5th (2.75 nm) harmonics, respectively. At 2.75 nm the 5th harmonic of the radiation reaches deep into the water window, a wavelength range that is crucially important for the investigation of biological samples

[en] This work discusses the behavior of electron bunch charge produced in an L-band normal conducting radio frequency gun from ${\mathrm{Cs}}_2\mathrm{Te}$ photocathodes illuminated with ps-long UV laser pulses and presumed homogeneous flattop laser transverse distribution. The measured charge shows the expected linear dependence in the quantum efficiency limited emission regime at low laser pulse energies. At higher laser pulse energy, the measured charge in the space charge limited emission regime should saturate, assuming an ideal homogeneous flattop laser transverse distribution. However, this behavior is not observed experimentally. Instead of saturating, the measured charge continues to increase with laser pulse energy, albeit with much weaker dependence than in the quantum efficiency limited emission regime. Simulations with the space charge particle tracking code ASTRA show that the charge saturates as expected using a homogeneous flattop laser transverse distribution. The discrepancy between simulations and measured excess charge may be attributed to the presence of unintentional Gaussian-like decaying radial halo beyond the core of the otherwise presumed homogeneous flattop core. The rate of increase of the measured charge at high laser pulse energies seems to be proportional to the amount of halo despite charge saturation in the core of the transverse laser radial profile. By utilizing core + halo particle distributions based on measured radial laser profiles, ASTRA simulations and semi-analytical emission models reproduce the behavior of the measured charge for a wide range of RF gun and laser operational parameters within the measurement uncertainties.

No abstract available

[en] We present a new method to determine the electron density of a plasma by measuring the periodicity of modulations introduced to the longitudinal phase space of a relativistic particle bunch by the interaction with the plasma via the self-modulation instability. As the modulation is solely depending on the plasma density and the beam parameters, this method allows to determine the time-resolved density of a plasma at the position of beam passage, which is confirmed in particle-in-cell simulations. Densities in the range of 3.6 × 10¹² cm⁻³ – 7.2 × 10¹⁵ cm⁻³ have been measured and the measurement accuracy is confirmed by comparison to spectroscopic plasma density measurements. (paper)

No abstract available

[en] The main goal of PITZ is the test and optimization of photo injectors for free electron lasers. PITZ generates electrons with an energy of about 5 MeV. To optimize the RF-gun parameters and to fulfill the requirements of the bunch compressor the longitudinal phase space behind the gun has to be studied. A measurement of the longitudinal phase space comprises a correlated measurement of momentum and temporal distribution. The momentum distribution is measured by deflecting the electron bunch using a spectrometer magnet. A subsequent Cherenkov radiator transforms the electron bunch into a light pulse with equal temporal and spatial distribution, which is imaged onto a streak camera by an optical transmission line to measure the longitudinal distribution. The longitudinal phase space was measured for different temporal photo cathode laser distributions, bunch charges and phases between RF field and laser. Physical effects in the dipole magnet, optical transmission line and streak camera, which influence the longitudinal phase space measurements, are taken into account. The measurement results were compared with simulations and with directly measured momenta and temporal distributions. (authors)

[en] An accelerator laboratory is presently under construction in Sofia at the Institute for Nuclear Research and Nuclear Energy. The laboratory will use a TR24 type of cyclotron, which provides a possibility to accelerate a proton beam with an energy of 15 to 24 MeV and current of up to 0.4 mA. An accelerator with such parameters allows to produce a large variety of radioisotopes for development of radiopharmaceuticals. The most common radioisotopes that can be produced with such a cyclotron are PET isotopes like: ¹¹C, ¹³N, ¹⁵O, ¹⁸F, ¹²⁴I, ⁶⁴Cu, ⁶⁸Ge/⁶⁸Ga, and SPECT isotopes like: ¹²³I, ¹¹¹In, ⁶⁷Ga, ⁵⁷Co, ^99mTc. Our aim is to use the cyclotron facility for research in the fields of radiopharmacy, radiochemistry, radiobiology, nuclear physics, materials sciences, applied research, new materials and for education in all these fields including nuclear energy. Presently we perform investigations in the fields of target design for production of radioisotopes, shielding and radioprotection, new ion sources etc. (paper)

[en] A generalization of an earlier proposed version of the Differential decay curve method is presented for the analysis of Doppler-shift attenuation lifetime measurements. The lifetime is derived directly from the line shapes of the depopulating and feeding transitions without any assumptions about or fitting of the time dependence of the population of the corresponding levels except for unobserved feeding when relevant. Fitting of the line shapes is also not necessary. The only approximation involved is related to the continuous treatment of the nuclear scattering events in the Monte Carlo simulation needed. Tests with simulated and real data reveal good reliability of this method. We propose also a new precise procedure where the lifetime is derived by fitting the time dependence of the population of the level of interest using the line shape of the depopulating transition and the difference of the spectra of the depopulating and feeding transitions. Practical application to simulated and real data proves the applicability of the new procedure