Inertial Fusion Driver Research Articles

Utilization of the Cu–Cl thermochemical cycle for hydrogen production using a laser driver thorium molten salts

In this paper, neutronic analysis and hydrogen production potential of a laser inertial fusion driver (LIFE) fueled molten salt thorium was investigated. Neutronic calculations were performed with MCNP code. The thorium molten salt was investigated both in six different ratios (2% ThF4 – 98% Li2BeF4 coolant, 4% ThF4 – 96% Li2BeF4, 6% ThF4 – 94% Li2BeF4, 8% ThF4 – 92% Li2BeF4, 10% ThF4 – 90% Li2BeF4, 12% ThF4 – 88% Li2BeF4) and two different fuel zone thickness (50–100 cm). In addition, 6Li enrichment (in 15–25-50-75 and 90% vol. ratios) in molten salts were examined effect to neutronic performance. As a result of the neutronic assessments, hydrogen production potential of the laser driver fusion breeder was investigated by using three step copper chlorine (Cu–Cl) cycle that one of the thermochemical water splitting methods. As a result, it was observed that tritium-breeding ratio (TBR) increased with increasing fuel zone thickness and 6Li enrichment, and it decreased with increasing ThF4 ratio. The energy multiplication value (M) has changed in direct proportion to fuel zone thickness, 6Li enrichment and ThF4 ratio. Since produced hydrogen mass flow depend on energy multiplication value, the highest hydrogen mass flow rate (m˙H2) was observed in option 100 cm fuel zone thickness, 12% ThF4 ratio and 90% ratio 6Li enrichment.

A massive-ion beam driver for high-energy-density physics and future inertial fusion

Several heavy ion drivers for heavy ion inertial fusion have been proposed in the US and Europe, based on linear induction accelerator technology [1] and existing RF technology [2], respectively, although they have not been realized on a large scale. Developing accelerator technology may provide an alternative efficient, robust, and relatively cheap massive-ion beam driver for future particle beam inertial fusion. Here, we propose an accelerator complex for accelerating giant cluster ions, instead of lead or bismuth ions, toward 120 GeV by using induction acceleration over the entire energy region. The proposed two-way multiplex induction synchrotron that is the main accelerator for the giant cluster ion beam would be equivalent to 10 synchrotrons of the same size for a single beam.

Production of radical species by electron beam deposition in an ArF* lasing medium

The electron-beam-pumped ArF laser is a laser technology capable of providing very high lasing energies at the shortest wavelength (λ = 193 nm) among the rare gas halide lasers and therefore has the potential to be a superior driver for inertial fusion. The electron kinetics are rigorously treated by numerically solving the steady-state, spatially averaged electron Boltzmann equation in Ar-F2 gas. The e-beam energy deposition and collisional reaction rates with electrons are calculated from the electron energy distribution function for a wide range of e-beam deposition powers (Pbeam = 10 kW/cm3–3 MW/cm3) and fluorine concentrations (xF2 = 0.01 – 10%). The rates are reduced to a set of coefficients that are fitted with analytical formulas as a function of two universal parameters: Pbeam/p and xF2, where p is the gas pressure. It is found that in the regime of high e-beam power deposition, the fluorine molecules are rapidly destroyed through dissociative attachment and neutral dissociation. The loss of F2 over the duration of the beam is proportional to the e-beam energy deposition per unit volume, εbeam, and follows ΔnF2(cm−3)≅4×1017εbeam(J/cm3), in agreement with experimental data. The fluorine molecule conversion to other fluorine species, including atomic fluorine, is shown to have a very small effect on the index of refraction even at percent level concentrations.

Numerical analysis corresponding with experiment in compact beam simulator for heavy ion inertial fusion driver

Tune depression in a compact beam equipment is estimated, and numerical simulation results are compared with an experimental one for the compact beam simulator in a driver of heavy ion inertial fusion. The numerical simulation with multi-particle tracking is carried out, corresponding to the experimental condition, and the result is discussed with the experimental one. It is expected that the numerical simulation developed in this paper is useful tool to investigate the beam dynamics in the experiment with the compact beam simulator.

Preliminary result of rapid solenoid for controlling heavy-ion beam parameters of laser ion source

AbstractTo realize a heavy-ion inertial fusion (HIF) driver, we have studied a possibility of laser ion source (LIS). A LIS can provide high-current high-brightness heavy-ion beams; however, it was difficult to manipulate the beam parameters. To overcome the issue, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The rapid ramping magnetic field could enhance limited time slice of the current and simultaneously the beam emittance changed accordingly. This approach may also be useful to realize an ion source for HIF power plant.

Development of high intensity linear accelerator for heavy ion inertial fusion driver

In order to verify the direct plasma injection scheme (DPIS), an acceleration test was carried out in 2001 using a radio frequency quadrupole (RFQ) heavy ion linear accelerator (linac) and a CO2-laser ion source (LIS) (Okamura et al., 2002) [1]. The accelerated carbon beam was observed successfully and the obtained current was 9.22mA for C4+. To confirm the capability of the DPIS, we succeeded in accelerating 60mA carbon ions with the DPIS in 2004 (Okamura et al., 2004; Kashiwagi and Hattori, 2004) [2,3]. We have studied a multi-beam type RFQ with an interdigital-H (IH) cavity that has a power-efficient structure in the low energy region. We designed and manufactured a two-beam type RFQ linac as a prototype for the multi-beam type linac; the beam acceleration test of carbon beams showed that it successfully accelerated from 5keV/u up to 60keV/u with an output current of 108mA (2×54mA/channel) (Ishibashi et al., 2011) [4]. We believe that the acceleration techniques of DPIS and the multi-beam type IH-RFQ linac are technical breakthroughs for heavy-ion inertial confinement fusion (HIF). The conceptual design of the RF linac with these techniques for HIF is studied. New accelerator-systems using these techniques for the HIF basic experiment are being designed to accelerate 400mA carbon ions using four-beam type IH-RFQ linacs with DPIS. A model with a four-beam acceleration cavity was designed and manufactured to establish the proof of principle (PoP) of the accelerator.

Plasma–wall interaction in laser inertial fusion reactors: novel proposals for radiation tests of first wall materials

Dry-wall laser inertial fusion (LIF) chambers will have to withstand strong bursts of fast charged particles which will deposit tens of kJ m−2 and implant more than 1018 particles m−2 in a few microseconds at a repetition rate of some Hz. Large chamber dimensions and resistant plasma-facing materials must be combined to guarantee the chamber performance as long as possible under the expected threats: heating, fatigue, cracking, formation of defects, retention of light species, swelling and erosion. Current and novel radiation resistant materials for the first wall need to be validated under realistic conditions. However, at present there is a lack of facilities which can reproduce such ion environments.This contribution proposes the use of ultra-intense lasers and high-intense pulsed ion beams (HIPIB) to recreate the plasma conditions in LIF reactors. By target normal sheath acceleration, ultra-intense lasers can generate very short and energetic ion pulses with a spectral distribution similar to that of the inertial fusion ion bursts, suitable to validate fusion materials and to investigate the barely known propagation of those bursts through background plasmas/gases present in the reactor chamber. HIPIB technologies, initially developed for inertial fusion driver systems, provide huge intensity pulses which meet the irradiation conditions expected in the first wall of LIF chambers and thus can be used for the validation of materials too.

Effective Parameters on the Energy Gain of Ignited Fuel

The minimum energy needed to ignite a D/3He capsule is a considerable problem in the optimization of an inertial fusion driver. The minimum energy depends on the driver efficiency and the capsule drive pressure. This dependence is examined using a series of numerical simulations to find ignited capsules which have different values of the driver efficiency, isentrope parameter and drive pressure. The goal of this article is an appropriate description of the main parameter at high energy gain. With 1,000 MJ laser irradiation and the coupling efficiency of 10%, it is found that attaining a quasi-isobaric state with a temperature of 14 keV and areal density value of 80 g/cm2 for the D/3He fuel would suffice to obtain a target gain of 50–60 required for the D/3He reactor.

On the use of KrF lasers for fast ignition

AbstractThe KrF laser has been considered as an inertial fusion driver alternative to diode-pumped lasers. The possibilities of KrF lasers for fast ignition is supported by their short wavelength and the corresponding larger penetration depth together with the possible use of the same amplifiers for fusion driver and fast ignitor. It is shown that in the case of a fusion test facility both the energy and the intensity requirements can be fulfilled. A fast ignitor using 20 ps KrF pulses requires beam smoothing techniques after angular multiplexing due to the coherence of the beam. A multiple beam fast ignitor is suggested as an alternative in which a high number of beams of 1 ps duration are separately focused on the fuel after polarization demultiplexing. This arrangement allows even the pulse-forming of the ignitor.

New amplifying laser concept for inertial fusion driver

This paper presents a new amplifying laser concept designed to produce high energy in either short or long pulses using coherent or incoherent addition of few millions fibers. These are called respectively CAN for Coherent Amplification Network and FAN for Fiber Amplification Network. The fibers would be large core or Large Mode Area (LMA) which have demonstrated up to 10, mJ output energy per fiber1. Such a system could meet the driver criteria of Inertial Fusion Energy (IFE) power plants based on Inertial Confinement Fusion (ICF), in particular high efficiency and high repetition rate.

Development of cryogenic TGG ceramic based Faraday rotator for inertial fusion driver

As the first demonstration of Faraday effect with a TGG ceramics, the Verdet constant was experimentally evaluated to be 36.4 rad/Tm at 1053 nm, which is same as that of the single crystal. The Verdet constant was improved for 87 times greater than that at room temperature. The measured thermal conductivity was corresponding to TGG single crystal between 100 K and room temperature. We have confirmed the feasibility of Faraday material for IFE driver by use of cryogenic TGG ceramics.

Studies on heavy ion fusion and high energy density physics in Japan

In this paper, significant progresses of Japanese research activities are presented in heavy ion fusion (HIF) and high energy density physics (HEDP). Heavy ion beam (HIB) is a prominent tool to study HEDP and HIF, and HIBs may be a promising inertial fusion driver. HIB accelerators have been studied intensively for a long time; HIB pulse profile, a particle energy and a HIB quality are controllable. A HIB energy deposition profile is also well defined, and HIB energy is deposited inside a material. By focusing and using the HIB excellent properties, Japanese HIF and HEDP activities have covered a wide variety of subjects ranging from new accelerators to future HIF studies: ion source, new inductive accelerator, beam physics, beam bunching, beam instabilities, HIB interactions with gas or materials, laser ion acceleration, HIB transport, HIB-based warm dense (WD) state generation, new measurement of HED or WD matters, HIB stopping power, atomic physics, multi-HIBs illumination on a target, HIF target implosion, impact ignition scheme, HIB-radiation conversion, radiation confinement and transport in HED matter or in HIF, and so on.

Optimization of a 3<tex>$times$</tex>3 Focusing Array for Heavy Ion Drivers

A heavy ion driver for inertial fusion will accelerate an array of beams through common induction cores and then direct the beams onto the DT target. An array of quadrupole focusing magnets is used to prevent beam expansion from space charge forces. In the array, the magnet fields from the coils embracing the beams are coupled, which reduces the cost of superconductor and increases the focusing power. The challenges in designing such an array are meeting the strict requirements for the quadrupole field inside the beam pipes and preventing stray fields outside. We report our optimization effort on designing such an array and show that 3 times 3 or larger arrays are feasible and practical to build with flat racetrack coils

Commissioning of the University of Maryland Electron Ring (UMER): Advances toward multiturn operation

The University of Maryland Electron Ring (UMER) is a low-energy, high current recirculator for beam physics research [M. Reiser et al., in Proceedings of the 1999 Particle Accelerator Conference, New York, NY (IEEE, New York, 1999), p. 234]. Ring construction is completed for multiturn operation of beams over a broad range of intensities and initial conditions. UMER is an extremely versatile experimental platform with a beam current of up to 100mA and a pulse length as long as 100ns. UMER is addressing issues in beam physics relevant to many applications that require intense beams of high quality, such as advanced concept accelerators, free electron lasers, spallation neutron sources, and future heavy-ion drivers for inertial fusion. The primary focus of this paper is to present experimental results in the areas of beam steering and multiturn operation of the ring. Unique beam steering algorithms now include measurement of the beam response matrix at each quadrupole and matrix inversion by singular value decomposition. With these advanced steering methods, transport of an intense beam over four turns (144 full lattice periods) of the ring has been achieved.

Experimental study of the transport limits of intense heavy ion beams in the HCX

The High Current Experiment (HCX) at Lawrence Berkeley National Laboratory is part of the US program to explore heavy-ion beam transport at a scale representative of the low-energy end of an induction linac driver for fusion energy production. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge-dominated heavy-ion beams at high space-charge intensity (line charge density up to ∼0.2 μC/m) over long pulse durations (4 μs) in alternating gradient focusing lattices of electrostatic or magnetic quadrupoles. The experiment also contributes to the practical baseline knowledge of intense beam manipulations necessary for the design, construction and operation of a heavy ion driver for inertial fusion. This experiment tests transport issues resulting from nonlinear space-charge effects and collective modes, beam centroid alignment and beam steering, matching, image charges, halo, electron cloud effects, and longitudinal bunch control. We first present the results for a coasting 1 MeV K + ion beam transported through the first ten electrostatic transport quadrupoles, measured with optical beam-imaging and double-slit phase-space diagnostics. This includes studies at two different radial fill factors (60% and 80%), for which the beam transverse distribution was characterized in detail. Additionally, beam energy measurements will be shown. We then discuss the first results of beam transport through four pulsed room-temperature magnetic quadrupoles (located downstream of the electrostatic quadrupoles), where the beam dynamics become more sensitive to the presence of secondary electrons.

Scientific issues in future induction linac accelerators for heavy-ion fusion

The worldwide heavy-ion fusion effort has made a large amount of progress over almost three decades of research on the intense beam physics and concepts needed for an inertial fusion driver. In the 1970s, ‘80s, and ‘90s in the US, most experiments used driver parameters scaled to low energy and low line charge density in order to study, most often with a single beam, the physics of high-perveance beams. More recently, the US program has introduced higher line charge density experiments, where the beam space charge potential is significant. This allows investigation of the production, and effect on the beam, of stray electrons. Increasingly, the possibilities for neutralizing plasmas are also being investigated, both just upstream and in the target chamber. This talk will outline the scientific issues that remain to be examined. These include issues of longitudinal compression, dynamic aperture, electron/ion instabilities, effect of electrons and gas on the beam, longitudinal emittance evolution, halo production, inductive effects at high energy, multiple beams, innovative final focus approaches, and driver issues for solenoidal transport. An outline of future experiments to address these issues will be presented and discussed.

Beam experiments in the extreme space-charge limit on the University of Maryland Electron Ring

The University of Maryland Electron Ring (UMER), designed for transport studies of space-charge dominated beams in a strong focusing lattice, is nearing completion. UMER models, for example, the recirculator accelerator envisioned as a possible driver for heavy-ion inertial fusion. The UMER lattice will consist of 36 alternating-focusing (FODO) periods over an 11.5 m circumference. The main diagnostics are phosphor screens and capacitive beam position monitors placed at the center of each 20° bending section. In addition, pepper-pot and slit-wire emittance meters are in operation. We present experimental results for three cases of strong space-charge dominated transport (7.2, 24, and 85 mA, at 10 keV) and contrast them with one case in the emittance-dominated regime (0.6 mA at 10 keV). With focusing given by σ0=76°, the zero-current betatron phase advance per period, the range of currents corresponds to a space-charge tune depression of 0.2 to 0.8. This range is unprecedented for a circular machine. The beam physics over three transport distances is considered: at or near the source, over the length of the matching section (about 1 m), and single turn (10 m). Issues associated with beam characterization, scaling of various parameters, alignment, and envelope matching are discussed.

High current ion beam RF acceleration and perspectives for an inertial fusion driver

The actual situation with respect to the use of an RF linac driver for heavy ion inertial fusion (HIF) is discussed. At present, there is no high current heavy ion linac under construction. However, in the course of linac projects for e−, p, d, or highly charged ions several developments were made, which may have some impact on the design of a HIF driver. Medium- and low-β superconducting structures suited for pulsed high current beam operation are actually designed and investigated at several laboratories. A superconducting 40 MeV, 125 mA cw linac for deuteron acceleration is designed for the Inertial Fusion Material Irradiation Facility (IFMIF). The Institute for Applied Physics (IAP) is developing a superconducting 350-MHz, 19-cell prototype CH-cavity for β = 0.1. The prototype cavity will be ready for tests in 2004. A superconducting main HIF driver linac would considerably reduce the power losses. Moreover, it would allow for an efficient linac operation at a higher duty factor.The 1.4-AMeV room-temperature High Current Injector HSI at Gesellschaft für Schwerionenforschung (GSI) has been in routine operation for more than 2 years now. With a mass-to-charge ratio of up to 65, a current limit of 15 mA for U4+, and an energy range from 2.2 AkeV up to 1.4 AMeV, this linac is suited to gain useful experience on the way toward the design of a HIF RF driver. The status and technical improvements of that A/q ≤ 65, 91-MV linac are reported. Beam dynamics calculations for Bi1+-beams show that powerful focusing elements at the linac front end are the bottleneck with respect to a further increase in beam current. Besides superconducting and pulsed wire quadrupoles, the potential of the Gabor-plasma lenses is investigated.

Experiments with space-charge-dominated beams for heavy ion fusion applications

A detailed understanding of the physics of space-charge-dominated beams is vital in the design of heavy ion inertial fusion (HIF) drivers. In that regard, low-energy, high-intensity electron beams provide an excellent model system. The University of Maryland Electron Ring (UMER), currently being installed, has been designed to study the physics of space-charge-dominated beams with extreme intensity in a strong focusing lattice with dispersion. At 10 keV and 100 mA, the beam from the UMER injector has a generalized perveance as much as 0.0015, corresponding to that of proposed HIF drivers. Though compact (11 m in circumference), UMER will be a very complex device by the time of its completion (expected 2003). We present an update on the construction as well as recent experimental results.

Performance of the K+ ion diode in the 2 MV injector for heavy ion fusion

Heavy ion beam inertial fusion driver concepts depend on the availability and performance of high-brightness high-current ion sources. Surface ionization sources have relatively low current density but high brightness because of the low temperature of the emitted ions. We have measured the beam profiles at the exit of the injector diode, and compared the measured profiles with EGUN and WARP-3D predictions. Spherical aberrations are significant in this large aspect ratio diode. We discuss the measured and calculated beam size and beam profiles, the effect of aberrations, quality of vacuum, and secondary electron distributions on the beam profile.