Radioactive ion beam development in Berkeley

Two radioactive ion beam projects are under development at the 88" Cyclotron, BEARS (Berkeley Experiment with accelerated radioactive species) and the 14O experiment. The projects are initially focused on the production of 11C and 14O, but it is planned to expand the program to 17F, 18F, 13N and 76Kr. For the BEARS project, the radioactivity is produced in form of either CO2 or N2O in a small medical 10 MeV proton cyclotron. The activity is then transported through a 300 m long He-jet line to the 88" cyclotron building, injected into the AECR-U ion source and accelerated through the 88" cyclotron to energies between 1 to 30 MeV/ nucleon. The 14O experiment is a new experiment at the 88" cyclotron to measure the energy-shape of the beta decay spectrum. For this purpose, a target transfer line and a radioactive ion beam test stand has been constructed. The radioactivity is produced in form of CO in a hot carbon target with a 20 MeV 3He from the 88" Cyclotron. The activity diffuses through an 8m long stainless steel line into the 6 GHz ECR ion source IRIS (Ion source for Radioactive ISotopes). It is then ionized and accelerated to 30 keV to mass separate the 14O and then implanted into a carbon foil. In order to optimize the on-line efficiencies of the LBNL ECR ion sources, off-line ionization efficiency studies are carried out for various gases. A summary of the ionization efficiency measurements is presented

Progress report of the third Generation ECR ion source fabrication

Recent progress in the construction of the 3rd Generation ECR ion source at the 88" cyclotron in Berkeley is reported. Test results of a full scale prototype superconducting magnet structure, which has been described in the last ECR Ion Source Workshop, lead to an improved coil design for the 3rd Generation ECR ion source. Solenoids of the new design have been fabricated and exceeded the design field values without quench. The new sextupole coils are currently being wound and will be tested this summer. This magnet structure consists of three solenoids and six race track coils with iron poles forming the sextupole. It is described in the report along with the structural support and coil winding specifications. The coils are designed to generate a 4T axial mirror field at injection and 3T at extraction and a radial sextupole field of 2.4 T at the plasma chamber wall. The high axial magnetic field of the 3rd Generation ECR ion source influences ion beam extraction considerably and we have initiated simulations of the extraction and beam transport system in order to enhance transmission through the injection beam line of the 88" cyclotron

Design Study of the Extraction System of the 3rd Generation ECR Ion Source

A design study for the extraction system of the 3rd Generation super conducting ECR ion source at LBNL is presented. The magnetic design of the ion source has a mirror field of 4 T at the injection and 3 T at the extraction side and a radial field of 2.4 T at the plasma chamber wall. Therefore, the ion beam formation takes place in a strong axial magnetic field. Furthermore the axial field drops from 3 T to 0.4 T within the first 30 cm. The influence of the high magnetic field on the ion beam extraction and matching to the beam line is investigated. The extraction system is first simulated with the 2D ion trajectory code IGUN with an estimated mean charge state of the extracted ion beam. These results are then compared with the 2D code AXCEL-INP, which can simulate the extraction of ions with different charge states. Finally, the influence of the strong magnetic hexapole field is studied with the three dimensional ion optics code KOBRA. The introduced tool set can be used to optimize the extraction system of the super conducting ECR ion source

Use of a Deep Recurrent Neural Network to Reduce Wind Noise: Effects on Judged Speech Intelligibility and Sound Quality.

Despite great advances in hearing-aid technology, users still experience problems with noise in windy environments. The potential benefits of using a deep recurrent neural network (RNN) for reducing wind noise were assessed. The RNN was trained using recordings of the output of the two microphones of a behind-the-ear hearing aid in response to male and female speech at various azimuths in the presence of noise produced by wind from various azimuths with a velocity of 3 m/s, using the "clean" speech as a reference. A paired-comparison procedure was used to compare all possible combinations of three conditions for subjective intelligibility and for sound quality or comfort. The conditions were unprocessed noisy speech, noisy speech processed using the RNN, and noisy speech that was high-pass filtered (which also reduced wind noise). Eighteen native English-speaking participants were tested, nine with normal hearing and nine with mild-to-moderate hearing impairment. Frequency-dependent linear amplification was provided for the latter. Processing using the RNN was significantly preferred over no processing by both subject groups for both subjective intelligibility and sound quality, although the magnitude of the preferences was small. High-pass filtering (HPF) was not significantly preferred over no processing. Although RNN was significantly preferred over HPF only for sound quality for the hearing-impaired participants, for the results as a whole, there was a preference for RNN over HPF. Overall, the results suggest that reduction of wind noise using an RNN is possible and might have beneficial effects when used in hearing aids

Development of a high intensity sup 4 sup 8 Ca ion beam for the heavy element program

A high intensity sup 4 sup 8 Ca ion beam has been developed at the 88 Inch Cyclotron for the synthesis of sup 2 sup 8 sup 3 112 using the reaction sup 2 sup 3 sup 8 U( sup 4 sup 8 Ca, 3n). An ion beam intensity of approx 700 pnA was delivered on target, resulting in a total dose of 2 x 10 sup 1 sup 8 ions over a six day period. Since sup 4 sup 8 Ca is a very expensive and rare isotope minimal consumption is essential. Therefore a new oven [1] and special tantalum liner [2] have been developed for the AECR-U ion source during the last year to improve the metal ion beam efficiency. Both the LBL ECR and the AECR-U ion sources are built with radial access. Six radial slots between the sextupole magnet bars provide additional pumping and easy access to the plasma chamber for ovens and feedthroughs. Two types of radial ovens have been used at LBNL in the past, operating at temperatures up to 2100 C