High-power Target Research Articles

New high-power X-ray target from FEINFOCUS

New high-power X-ray target from FEINFOCUS

A long-wavelength target station for the spallation neutron source

The Spallation Neutron Source (SNS), a major new user facility for studies of the structure and dynamics of materials, funded by the US Department of Energy (DOE), is under construction at Oak Ridge National Laboratory (ORNL). Details about the project are available in a recent paper and on the SNS Web site [MRS Bull. 28 (12) (2003) 923]. A Long-Wavelength Target Station (LWTS) [Technical Concepts for a Long-Wavelength Target Station for the Spallation Neutron Source, Argonne National Laboratory Report ANL-02/16, Oak Ridge National Laboratory Report ORNL/SNS-TM-2001/163, November 2002. See also www.pns.anl.gov/related/] will complement the High-Power Target Station (HPTS) facility of the SNS and will build upon the significant investment in the remainder of the installation by providing important new scientific opportunities. For areas of science using the optimized long-wavelength beam lines, the LWTS will at least double the overall scientific capability of the SNS and provide for up to an order of magnitude performance gain over the initial HPTS. The fully equipped SNS has the prospect to offer capabilities for neutron-scattering studies of the structure and dynamics of materials with sensitivity, resolution, dynamic range, and speed that are unparalleled in the world. Preliminary assessments of the performance of the several instruments treated in detail in the body of the paper bear out this expectation. The LWTS concept has been developed in close consultation with the scientific community through a series of workshops and conferences jointly sponsored by DOE's Office of Basic Energy Science and the National Science Foundation. We describe the principal features of the LWTS concept, and provide a preliminary summary of some neutron scattering instruments suited to exploit the unique features of the LWTS. It remains to develop concepts and designs for a full suite of instruments that exploit the capabilities of LWTS, a process that has begun in collaboration with the scientific community.

Numerical design of a 20 MW lead–bismuth spallation target for an accelerator-driven system

A spallation target system is a key component to be developed for an accelerator-driven system (ADS). It is known that a 15–25 MW spallation target is required for the practical size of an ADS. Although there have been some design studies for small power spallation targets, that is, less than 10 MW, designs of high power target systems for ADS are relatively rare. The design of a 20 MW spallation target is very challenging because more than 60% of the beam power is deposited as heat in a small volume of the target system. In the present work, a numerical design study was performed to get optimal design parameters for a 20 MW spallation target for a 1000 MW ADS. The cylindrical beam tube and the hemispherical beam window were adopted in the basic target design concept with 1 GeV proton energy, and the thermal-hydraulic and the structural analyses were performed with the CFX and ANSYS codes. The beam window diameter and thickness were varied to find the optimal parameter set based on the design criteria: maximum lead–bismuth eutectic (LBE) temperature <500 °C, maximum beam window temperature <600 °C, maximum LBE velocity <2 m/s, and the maximum beam window stress <160 MPa. The results of the present study show that a 40 cm wide proton beam with a uniform beam profile should be adopted for the spallation target of 20 MW power. It was found that a 2.5 mm thick beam window is needed to sustain the mechanical load.

Design aspects of high-power targets

The design of high-power targets for production of intense beams of radioactive ions requires the following: a reliable determination of the power deposited, knowledge of the thermal properties of the materials incorporated in the design, and a comprehensive thermal analysis of designs to evaluate the conceptual approaches. From the thermal analysis, iterations in the design approaches can lead to effective target conceptual designs that can bypass a series of prototype tests. Emphasis will be made for conductive cooling approaches, for which comprehensive thermal conductivity data are required for all components. Additional thermal properties are needed if radiative cooling or shielding is incorporated in target concepts. The example is presented of a uranium/carbon target to produce fission-product activities, featuring sensitivities to power dissipation and thermal properties assumed in the analyses.

High-power production targets for the Super-FRS using a fast extraction scheme

Abstract The high-power production target of the Super-FRS [H. Geissel et al., these Proceedings] will be irradiated by very intense heavy-ion beams which will be delivered from the future SIS100/200 [An International Accelerator Facility for Beams of Ions and Antiprotons, GSI-Report, 2001] synchrotron facility at the Gesellschaft fur Schwerionenforschung (GSI) Darmstadt. This paper presents calculations of the thermodynamic and the hydrodynamic response of such a target, considering that a uranium ion beam with an energy of 1 GeV/u and an intensity of 10 12 particles will impinge within 50 ns on a solid carbon target with a thickness of 4 g/cm 2 . Due to the high beam intensity the target may be strongly heated and could be destroyed in a single shot. The purpose of this work is to investigate with the help of two-dimensional numerical simulations how one can minimize target heating and avoid traget destruction.

High power target developments at ISAC

TRIUMF, Canada’s national research facility for particle and nuclear physics is currently operating the ISAC facility. A high-energy proton beam from the H - TRIUMF cyclotron is used to generate short-lived radioactive species in a thick target. An ion source at the target creates a radioactive beam, which is then injected into the ISAC beam lines and accelerator system. The ISAC facility is designed to accept proton beam intensity up to 100 μA at 500 MeV. At present our target design can only sustains 40 μA at maximum. Beyond this point the target has to be cooled. A new target equipped with fins has been developed that may sustain proton beam up to 100 μA. The fined target has been tested off-line and a thermal simulation using ANSYS ® has been conducted and the results are reported here.

The Spallation Neutron Source High Power Target Station Moderator Performance: Calculations and Studies

We address recent progress in the continued neutronic design of the Spallation Neutron Source Target Station as regards moderator performance. The Spallation Neutron Source Target Station will receive 2 MW of 1 GeV protons at 60 Hz. This level of proton power offers unprecedented neutronic performance for pulsed neutron production for time-of-flight neutron scattering, as well as unprecedented challenges in providing such a performance. We report on the results of recent design optimization studies and the importance of carefully matching moderator performance characteristics to the needs of the neutron scattering instruments.

Production of low- and high-energy radioactive-ion beams by fragmentation

The physics opportunities made possible by beams of rare isotopes are among the richest available in nuclear science. The rare-isotope accelerator (RIA) now under development is an innovative accelerator that will define the state of the art for all such facilities. A novel aspect of the RIA project is the conversion of the most intense high-energy heavy-ion beams into both fast and reaccelerated exotic beams. Along with target fragmentation in next-generation high-power ISOL targets, RIA will use projectile fragmentation in a high-energy separator/gas-filled ion collector system to provide an extensive range of thermalized ions for reacceleration. In addition, a second high-energy separator will provide the same or larger range of ions for high-energy experiments. A brief overview of the RIA accelerator concept, the layout of the facility, and production techniques will be given along with information on the present R&D efforts in gaseous-ion collection.

Integral Experiment on Induced Radioactivity and Decay-Heat of Mercury with 14 MeV Neutrons

For spallation neuron target design, an accurate estimation of induced activity is strongly requested. Mercury is the most promising material for the high-power spallation target. An integral experiment on induced radioactivity and decay-heat was carried out using a small mercury assembly and a D-T neutron source (Fusion Neutronics Source) at Japan Atomic Energy Research Institute (JAERI). Mercury-oxide (HgO) powder wrapped with a plastic sheet was irradiated in the mercury assembly for 6.7 hours. After the irradiation, the induced activities were measured with HPGe detectors. The radioactive products of 197m, gHg, 199mHg, 203Hg, 198gAu and 199Au were identified in the measured gamma-ray spectra. For the decay-heat measurement, a whole-energy absorption detector, which consisted with a pair of BGO scintillators, was used. The measurements were performed at various cooling times from 2.5 hours to 110 days. Experimental results of the radioactivity and the decay heat were compared with the calculation with DCHAIN-SP 2001. It was shown that the calculation reproduced the experiment within the accuracy of 20% by using the activation cross section curves evaluated on the basis of our experimental cross section data.

Analytical calculations and Monte-Carlo simulations of a high-resolution backscattering spectrometer for the long wavelength target station at the Spallation neutron source

Using the Monte-Carlo simulation programs McStas and VITESS, we present the design principles of the proposed high-resolution inverse geometry spectrometer on the Spallation neutron source (SNS)—long wavelength target station (LWTS). LWTS will enable the combination of large energy and momentum transfer ranges with energy resolution. Indeed the resolution of this spectrometer lie between that routinely achieved by spin echo techniques and the design goal of the high-power target station (HPTS) backscattering spectrometer. This niche of energy resolution is interesting for the study of slow motions of large objects and we are led to the domain of large molecules—polymers and biological molecules.

Contributions from X-ray and gamma-ray observations

An intense beam of 26gAl has been developed for accelerated beam experiments at TRIUMF’s ISAC facility. Studies of the on-line production of Al radionuclides from thick silicon carbide targets have been performed as part of a program of beam development for astrophysical reaction studies at ISAC. While the release of short-lived Al nuclides from SiC was found to be slow, development of new target material forms and high-power target containers has allowed operation of SiC targets with proton currents of up to 70 μA on target. In addition, operation with the TRIUMF resonant ionization laser ion source (TRILIS) has produced 26gAl beam intensities of 5.1 × 1010 s−1.

When power does not corrupt: Superior individuation processes among powerful perceivers.

To examine whether powerful people fail to individuate the less powerful, the authors assigned participants to either a high-power or low-power role for a computer E-mail role play. In 3 studies, participants in the high-power role made decisions and determined the outcomes of interactions; low-power role players had no power and relied on high-power targets for outcome decisions. Studies I and 2 found that high-power perceivers better individuated low-power targets. Study 3 demonstrated that high-power role players' superior judgment can be impaired by including a task that directs their responsibility toward organizational rather than interpersonal concerns. In all, results suggest that the effect of power on social judgment may be more complex and multifaceted than has previously been acknowledged.

Radiation Shielding and Protection of the European Spallation Neutron Source (ESS)

The shielding and the radiation protection of high intensity spallation neutron sources as ESS has special features and importance compared to usual accelerator shielding and protection considerations. For the shielding we are interested in very thick shields, so small uncertainties e.g. in cross sections lead to large errors; we are interested in detailed predictions, such as accurate particle spectra over large energy ranges, and the geometries of interest are complex, e.g. shields with multiple beam holes. Containment of radioactivity for the high power target station is also a very important issue and has highest hazard. The different methods, which are used for designing the ESS shielding, are discussed. Comparison with performed measurements is also given.

Two meetings focus on spallation neutron source

The SNS Neutron Instrumentation Workshop and Oak Ridge Neutron Users Meeting were held in Knoxville, TN from November 9 to 11, 1998. Over 200 participants attended the meeting, which was jointly sponsored by the US Department of Energy (DOE) and the National Science Foundation (NSF). The purpose of the instrumentation workshop was primarily to discuss scientific community needs for instrumentation at the Spallation Neutron Source (SNS). Topics covered included: update on the current status and expected performance of the Spallation Neutron Source; priorities f o r the initial suite of ten instruments to be built at the high power target station as part of the SNS reference design; and the science case for a second targedinstrument suite optimized for long wavelength neutrons.

Development of a high-power water cooled beryllium target for use in accelerator-based boron neutron capture therapy.

In order for ABNCT (accelerator-based boron neutron capture therapy) to be successful, 10-16 kW or more must be dissipated from a target. Beryllium is well suited as a high-power target material. Beryllium has a thermal conductivity of 200 W/mK at 300 K which is comparable to aluminum, and it has one of the highest strength to weight ratios of any metal even at high temperatures (100 MPa at 600 degrees C). Submerged jet impingement cooling has been investigated as an effective means to remove averaged power densities on the order of 2 x 10(7) W/m2 with local power densities as high as 6 x 10(7) W/m2. Water velocities required to remove these power levels are in excess of 24 m/s with volumetric flow rates of nearly 100 GPM. Tests on a prototype target revealed that the heat transfer coefficient scaled as Re0.6. With jet-Reynolds numbers as high as 5.5 x 10(5) heat transfer coefficients of 2.6 x 10(5) W/m2K were achieved. With this type of cooling configuration 30 kW of power could be effectively removed from a beryllium target placed on the end of an accelerator. A beryllium target utilizing a proton beam of 3.7 MeV and cooled by submerged jet impingement could be used to deliver a dose of 13 RBE cGy/min mA to a tumor at a depth of 4 cm. With a beam power of 30 kW, 1500 cGy could be delivered in 14.2 min.

Possible developments of high power targets for radioactive beams

The development of the RIST tantalum foil target for the production of radioactive nuclei by bombardment with energetic (∼1 GeV) proton beams of high intensity (100 μA) has shown that targets capable of dissipating 20–60 kW of thermal power can be constructed. Tantalum is a good material for high power dissipation because, as a metal, it has a relatively good thermal conduction and is able to stand very high temperatures. However, for a full range of unstable beams, it will be necessary to have targets made from many different materials. Developments of high power target and ion source designs are discussed with particular emphasis on non-metallic, non-refractory powder and liquid target materials. Also, the possibilities of combining targets and ion sources to reduce effusion times are considered, as well as methods to increase the surface-desorption rates of the radioactive particles.

High power target measurements and finite element calculations for ISL targets

Methods for cooling thick spallation targets (emphasis is on targets for an ISL facility) to uniform temperatures are discussed along with methods for testing targets in a manner that does not require an accelerator facility or result in induced radioactivity. Empirical data is supplemented by computer models using a custom finite element analysis package which allows modeling of combined heat and fluid flow.

Neutron spallation sources in Europe

After a brief general and historical discussion, the main design features of spallation sources are described. At the present time, Europe not only has the world-leading pulsed neutron spallation source, the SNS-ISIS at RAL, UK, but it is on the point of commissioning a world-leading continuous cyclotron-driven source, the SINQ at PSI, Switzerland. Looking to the future, yet more powerful pulsed sources are actively under study and the difficult problem of high-power target design (>250 kW) is leading to a new technology for liquid targets. The accelerator designs, although basically classical, require custom-built solutions that are often at the limit of presentday accelerator technology.

The high power target system for SISSI, an intense source of secondary ions

In order to increase the collection efficiency of radioactive isotopes produced by the GANIL heavy ion beams impinging onto thick targets, a device named SISSi was designed to focus these beams on a 0.4 mm diameter spot. In view of the upcoming modification of the accelerator which will boost the beam intensities by a factor of 15, as well as for the present situation, a target had to be designed to reliably dissipate the high power deposited by the heavy ions on such a small area. The magnetic and cryogenic environment, along with the radiation and safety problems, were severe constraints in the design described below. Preliminary experimental results are given.

A high power target for the production of [ 18F] fluoride

A target for high yield production of aqueous [ 18F] fluoride at high beam currents has been developed for the 11 MeV Siemens/CTI RDS proton cyclotron at the University of Wisconsin. The silver body, gold backed target is characterized a small volume (400 μl) and is operated at high pressure (40 bar). The target yield is 79% of the theoretical maximum for beam currents up to 40 μA. The highest yield to date is 70 GBq. Target construction and performance are presented, and recent applications to PET radioisotope syntheses and radioactive beam production are discussed.