Most of the proposed electron accelerator projects for future FELs, ERLs or 4th generation light sources require electron beams with an unprecedented combination of high brightness, low emittance, and high average current. In all projects photoguns will be applied: DC-photoguns, normal conducting RF-photoguns (NC-guns), and superconducting RF photoguns (SRF-guns). While the concepts of DC- and NC-guns are well proofed, the SRF-gun development still possesses a high risk. Challenges are the design of the superconducting cavity, the choice of the photocathode type, its life time, a possible cavity contamination, the difficulty of coupling high average power into the gun, and, finally, the risk of beam excitation of higher-order cavity modes. In combination with SRF linacs, the SRF-guns seem to be the best solution for high average currents. Several R&D projects of SRF-gun have been launched. In this paper, we will give an overview of the progress of the SRF photoinjector development. In detail, the technical concept, the performance and the status of the Dresden Rossendorf SRF-gun project, a collaboration of BESSY, DESY, MBI and FZD, will be presented. The main design parameters of this SRF-gun are the final electron energy of 9.5MeV, 1mA average current, and transverse normalized emittances (rms) of 1mmmrad at 77pC and 2.5mmmrad at 1nC bunch charge. The 1.3GHz cavity consists of three TESLA-shaped cells, a specially designed half-cell where the photocathode is placed and a choke filter in order to prevent RF losses at the cathode side. The normal-conducting photocathode with a Cs2Te photoemission layer is cooled by liquid nitrogen. The SRF-gun cryostat consists of a stainless steel vacuum vessel, a warm magnetic shield, a liquid nitrogen-cooled thermal shield and a titanium He tank with a two-phase supply tube. The 10kW fundamental power coupler is adopted from the ELBE cryomodule. In a first commissioning and test period the gun will be operated in parallel to the accelerator. A diagnostic beamline will allow beam parameter measurement and further optimization of the SRF-gun. In a final step, the gun will be connected to the ELBE superconducting linear accelerator to deliver an improved electron beam to the user labs.

A superconducting radio frequency (RF) photoelectron injector (SRF gun) is under development at the Research Center Dresden–Rossendorf. This project aims mainly at replacing the present thermionic gun of the superconducting electron linac ELBE. Thereby the beam quality is greatly improved. Especially, the normalized transverse emittance can be reduced by up to one order of magnitude depending on the operating conditions. The length of the electron bunches will be shortened by about two orders of magnitude making the present bunchers in the injection beam line dispensable. The maximum obtainable bunch charge of the present thermionic gun amounts to 80pC. The SRF gun is designed to deliver also higher bunch charge values up to 2.5nC. Therefore, this gun can be used also for advanced facilities such as energy recovery linacs (ERLs) and soft X-ray FELs. The SRF gun is designed as a 312 cell cavity structure with three cells basically TESLA cells supplemented by a newly developed gun cell and a choke filter. The exit energy is projected to be 9.5MeV. In this paper, we present a description of the design of the SRF gun with special emphasis on the physical and technical problems arising from the necessity of integrating a photocathode into the superconducting cavity structure. Preparation, transfer, cooling and alignment of the photocathode are discussed. In designing the SRF gun cryostat for most components wherever possible the technical solutions were adapted from the ELBE cryostat in some cases with major modifications. As concerns the status of the project the design is finished, most parts are manufactured and the gun is being assembled. Some of the key components are tested in special test arrangements such as cavity warm tuning, cathode cooling, the mechanical behavior of the tuners and the effectiveness of the magnetic screening of the cavity.

At the Forschungszentrum Rossendorf the development and the setup of the 2 nd superconducting radio frequency photo electron injector (SRF-Photo-Gun) is nearly completed. In this report we present the results of the cavity treatment. The warm tuning was carried out considering pre-stressing and the tuning range of both tuners (half cell and full cells). The optimal antenna length of the main coupler and both fundamental pickups were determined by practical external Q studies. Furthermore the characteristic tuning curves of the choke filter and both HOM filters were simulated, measured and tuned at the pi-mode frequency. The preparation (etching and rinsing) and the vertical cold test were done at DESY.

The designs and a report on the progress in construction and testing of the cryomodule and the tuning system for the SRF gun are presented. The SRF gun project, a collaboration of BESSY, DESY, MBI and FZR, aims at the installation of a CW photo injector at the ELBE linac. The cryostat consists of a stainless steel vacuum vessel, a warm magnetic shield, a liquid N cooled thermal shield, and a He tank with two-phase supply tube. A heater pot in the He input port will be used for He level control. The 10 kW power coupler is adopted from the ELBE module. A cooling and support system for the NC photo cathode has been developed and tested. It allows the adjustment of the cathode with respect to the cavity from outside. The cryomodule will be connected with the 220 W He refrigerator of ELBE and will operate at 1.8 to 2 K. The static thermal loss is expected to be less than 20 W. Two tuners will be installed for separate tuning of the three TESLA cells and the half-cell. The tuners are dual spindle-lever systems with step motors and low-vibration gears outside the cryostat. Functionality, tuning range and accuracy have been tested in cryogenic environment.

After successful tests of a SRF gun with a superconducting half-cell cavity a new SRF photoinjector for cw operation at the ELBE linac is under development. The paper discuss the design of the injector, the technological challenges of different components, the status of manufacturing and the expected parameters.

A superconducting rf photo electron injector (SRF gun) is under development at the Forschungszentrum Rossendorf. The project aims at several issues: improvement of beam quality for the ELBE superconducting electron linac, demonstration of feasibility of this gun type, investigation of critical components, and parameter studies for future application . In 2005 - 2006, a substantial progress has been made. The two 3½-cell niobium cavities for the gun have been delivered from the company ACCEL. The main parts for gun cryostat like vacuum vessel, cryogenic and magnetic shields are ready. Test benches for the cathode cooling system and the cavity tuner are being assembled. The photo cathode preparation lab has been arranged, and the diagnostic beam line has been designed. After delivery of the gun cavities, their RF properties are being measured at room temperature and the warm tuning is being carried out.

This paper presents results of the photocathode cooling system test of the 312 cell SRF gun at the Forschungszentrum Rossendorf. The SRF gun will produce short electron pulses with high bunch charges and low transverse emittance. The requirement for the superconducting electron linear accelerator in Rossendorf (ELBE) is to provide a low emittance electron beam up to 1mA current and 9.5MeV energy. Additionally, it will easily operate in continuous wave (cw) mode because of the low RF power losses in the superconducting material. Therefore, the normal conducting copper cathode must be cooled by liquid nitrogen in order to preserve the temperature of the cavity at 2.2K. The estimated power input from the RF field into the cathode could be more than 10W [P. vom Stein, Thesis, TU-Dresden, 1998]. First results of temperature measurements of the photocathode, respectively, from the cooling system at a heat load up to 30W are presented.

In the paper, we report on the status and progress of the superconducting RF gun project in Rossendorf. The gun is designed for cw operation mode with 1 mA current and 9.5 MeV electron energy, and it will be installed at the ELBE superconducting electron linear accelerator. The gun will have a 3½ cell niobium cavity operating at 1.3 GHz. The cavity consists of three cells with TESLA geometry and a specially designed half- cell in which the photocathode will be placed. The production of two Nb cavities, with RRR 300 and 40 respectively, has be finished at the beginning of 2005. After delivery, the RF tests will be performed and the preparation of the cavities will be started. At the same time, the design of the cryostat and the fabrication of its components are already finished. Further activities are the design of the diagnostic beam line, the testing of the new photocathode preparation system, and the upgrade of the 262 nm driver laser system. electron source with high average current and low emittance for the ELBE superconducting linear accelerator and to demonstrate the capability for the future applications in FEL light sources and energy recovery linacs. This new gun can generate short pulses and high-brightness electron beams, as known from the conventional photo-injectors. Moreover, the use of the superconducting cavity allows the cw-mode operation and thus high average currents. In the proof-of- principle experiment, the operation of such a photo- injector with a half-cell cavity was successfully demonstrated (1). During about 200 hour's operation, no phenomenon of quality factor depression was observed.

In the paper, we report on the status and progress of the superconducting RF gun project in Rossendorf. The gun is designed for cw operation mode with 1 mA current and 9.5 MeV electron energy, and it will be installed at the ELBE superconducting electron linear accelerator. The gun will have a 3 1/2 cell niobium cavity operating at 1.3 GHz. The cavity consists of three cells with TESLA geometry and a specially designed half-cell in which the photocathode will be placed. The production of two Nb cavities, with RRR 300 and 40 respectively, leas be finished at the beginning of 2005. After delivery, the RF tests will be performed and the preparation of the cavities will be started. At the same time, the design of the cryostat and the fabrication of its components are already finished. Further activities are the design of the diagnostic beam line, the testing of the new photocathode preparation system, and the upgrade of the 262 nm driver laser system.

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Ten healthy volunteers, 12 classic phenylketonuria (PKU) heterozygotes, and 5 classic phenylketonurics have been loaded orally with a mixture of 5 μCi of l-[U-14C]phenylalanine plus 25 mg/kg of l-[2H5]phenylalanine. For 3 h thereafter, carbon-14 activity in expired air and total carbon dioxide were measured continuously and the levels of l-phenylalanine and l-tyrosine in plasma were determined in six blood samples. After 3 h, 15.1 ± 2.1% of the applied dose of radioactivity was recovered in the expired air of the healthy subjects, compared to 10.1 ± 2.2% for PKU heterozygotes and 0.32 ± 0.18% for classic phenylketonurics. The integrated activity expired provides a discrimination between normals and PKU heterozygotes with a classification error of about 13% compared to an error of about 9% based on the fasting l-phenylalanine over l-tyrosine ratio. A combination of these two parameters in a two-dimensional discriminatory analysis reduces the classification error to < 1%.

Four normal and five aldehyde dehydrogenase (ALDH) isozyme I deficient individuals were subsequently loaded with (1-13C)ethanol and (1-13C)sodium acetate and the conversion of the label to 13CO2 was determined in expired air by isotope ratio mass spectrometry. In the 13C-acetate breath test, both groups showed virtually identical recovery of the label in expired air, namely 48.5±2.3% (mean±S.D.) for normal and 46.8±5.7% for deficient individuals. However, in the 13C-ethanol breath test, both the groups performed differently. On average, although a certain overlap of the single data was observed, the recovery of the label after four hours was 43.4±3.8% for the normal and 35.6±6.8% for the ALDH deficient subjects. These findings suggest a slower conversion of ethanol to carbon dioxide in aldehyde dehydrogenase deficient individuals, which may be another consequence of this deficiency besides the higher plasma acetaldehyde levels observed after ethanol loading in comparison to individuals with normal aldehyde dehydrogenase activity.

Oral loading with 1.5 g of l-[15N]phenylalanine was performed simultaneously with an intravenous infusion of 1.5 g of l-[2H5]phenylalanine in two healthy volunteers with normal phenylalanine-hydroxylase activity. For both volunteers peak levels of oral l-[15N]phenylalanine were about 20 μg/ml compared to peak levels of around 50 μg/ml for intravenous l-[2H5]phenylalanine. Throughout the four hours following application, the plasma levels of the intravenously administered phenylalanine were higher than the plasma levels of the phenylalanine administered orally. In contrast, similar plasma levels of l-[15N]tyrosine and of l-[2H4]tyrosine formed in vivo by hydroxylation of the corresponding stable isotope labelled l-phenylalanine precursors were observed during the test, indicating that about equal fractions of both the oral and of the intravenous l-phenylalanine are converted into l-tyrosine.

The glucuronide conjugates of the two isomeric antipyrine phase I metabolites of antipyrine in man, 4-hydroxyantipyrine and 3-hydroxymethylantipyrine have been analysed by field desorption and fast atom bombardment mass spectrometry. These isomers could be clearly distinguished on the basis of their fragmentation behaviour which was found to correlate with that observed under pyrolysis electron impact conditions.

Oral loading with 25 mg/kg of pentadeuterated L-phenylalanine has been used for the discrimination between normozygous subjects and carriers for phenylketonuria. The test provides five types of data derived from plasma Phe and Tyr concentrations on which the discrimination can be based: fasting phenylalanine/tyrosine ratios, total Phe levels, total Phe/total Tyr ratios, absolute L-[2H5]phenylalanine plasma levels, and L-[2H5]Phe/L-[2H4]Tyr ratios. Absolute L-[2H4]Tyr and total L-Tyr concentrations provide the poorest discrimination with statistical classification errors around 30%. The corresponding classification error of fasting Phe/fasting Tyr ratios was circa 13%, and both labelled Phe/labelled Tyr and total Phe/total Tyr concentration ratios gave minimal errors below 2%.

AbstractCarbon‐14 and tritium labelled ionic organic compounds such as quaternary ammonium salts, steroid sulphates, bile acid conjugates, and oligopeptides have been analyzed for their label distribution and for their specific radioactivity by fast atom bombardment and field desorption mass spectrometry. No significant differences between the quantitative results with both techniques are found. The minimal specific radioactivities detectable by this approach are about 20 MBq mmol−1 or 10 GBq mmol−1 for compounds labelled with one atom of carbon‐14 or one atom of tritium per molecule, respectively. Specific radioactivity determinations of highly labelled biochemicals are characterized by a precision and an accuracy in the region between 1% and 5%.