The Heavy Ion Fusion Virtual National Laboratory Highly Compressed Ion Beams for Warm Dense Matter Science * Alex Friedman 1,2, John J. Barnard 1,2, Richard J. Briggs 7, Debra A. Callahan 2, George J. Caporaso 2, C. M. Celata 1,3, Ronald C. Davidson 1,4, Andris Faltens 1,3, Larry Grisham 1,4, David P. Grote 1,2, Enrique Henestroza 1,3, Igor Kaganovich 1,3, Edward P. Lee 1,3, Richard W. Lee 2, Matthaeus Leitner 1,3, B. Grant Logan 1,3, Scott D. Nelson 2, Craig Olson 1,5, Gregg Penn 3, Lou Reginato 1,3, Tim Renk 5, David Rose 6, Andrew Sessler 1,3, John W. Staples 1,3, Max Tabak 2, Carsten Thoma 6, William Waldron 1,3, Dale R. Welch 6, Jonathan Wurtele 3, Simon S. Yu 1,3 1. Heavy Ion Fusion Virtual National Laboratory 2. Lawrence Livermore National Laboratory, University of California, Livermore CA 3. Lawrence Berkeley National Laboratory, University of California, Berkeley CA 4. Princeton Plasma Physics Laboratory, Princeton NJ 5. Sandia National Laboratories, Albuquerque NM 6. Voss Scientific, LLC, Albuquerque NM 7. Science Applications International Corporation, Alamo CA *Work performed under auspices of USDOE by U. of CA LLNL & LBNL, PPPL, and SNL, under Contract Nos. W-7405-Eng-48, DE-AC03- 76SF00098, DE-AC02-76CH03073, and DE-AC04-94AL85000, and by ATK and SAIC. Presentation No. BP th Annual Meeting of the APS Division of Plasma Physics, Denver, Oct , 2005

The Heavy Ion Fusion Virtual National Laboratory Abstract The Heavy Ion Fusion Virtual National Laboratory is developing the intense ion beams needed to drive matter to the High Energy Density regimes required for Inertial Fusion Energy and other applications. An interim goal is a facility for Warm Dense Matter studies, wherein a target is heated volumetrically without being shocked, so that well-defined states of matter at 1 to 10 eV are generated within a diagnosable region. In the approach we are pursuing, low to medium mass ions with energies just above the Bragg peak are directed onto thin target “foils,” which may in fact be foams with mean densities 1 to 10 percent of solid. This approach complements that being pursued at GSI Darmstadt, wherein high-energy ion beams deposit a small fraction of their energy in a cylindrical target. We present the beam requirements for Warm Dense Matter experiments. We discuss neutralized drift compression and final focus experiments and modeling. We describe suitable accelerator architectures based on Drift-Tube Linac, RF, single-gap, Ionization-Front Accelerator, and Pulse- Line Ion Accelerator concepts. The last of these is being pursued experimentally. Finally, we discuss plans toward a user facility for target experiments.

The Heavy Ion Fusion Virtual National Laboratory Outline High Energy Density Physics (HEDP); Warm Dense Matter regime Beam requirements Experiments & modeling –Neutralized focusing –Neutralized pulse compression Accelerator Plans

The Heavy Ion Fusion Virtual National Laboratory High Energy Density Physics is now a mission of the Heavy Ion Fusion VNL Long-term goal remains Inertial Fusion Energy (IFE) Emerging interest in HEDP  near-term HIF effort focused on HEDP IFE is HEDP, but we now need to heat targets in the near term –HEDP is  J/m 3 ;  p  hydro time ~ 1 ns –Not yet accessible with our ion drivers; must develop capability “Warm Dense Matter” (WDM) regime of strongly-coupled few-eV plasmas at to of solid density is the first step –Interesting, and challenging, because these are neither classical plasmas nor ordinary condensed matter Ion-driven HEDP J. J. Barnard, Poster LP1.80, 2:00 Wed.; see also PAC05 proceedings

The Heavy Ion Fusion Virtual National Laboratory The  - T regime accessible by beam driven experiments is that of the interiors of gas planets and low-mass stars Accessible region using beams in near term Region is part of Warm Dense Matter (WDM) regime WDM lies at crossroads of degenerate vs. classical and strongly coupled vs. weakly coupled Figure adapted from “Frontiers in HEDP: the X-Games of Contemporary Science:” Terrestial planet

The Heavy Ion Fusion Virtual National Laboratory R. More: Large uncertainties in WDM region arise in the two phase (liquid-vapor) region Accurate results in two-phase regime essential for WDM R. More has recently developed new high-quality EOS for Sn Interesting behavior in the T~1.0 eV regime EOS tools for this temperature and density range are just now being developed. P (J/cm 3 ) T (eV)  (g/cm 3  Critical point unknown for many metals, such as Sn R. Lee plot, showing contours of fractional pressure difference between two common EOS’s for Al New theoretical EOS work meshes very well with the experimental capabilities we are creating

The Heavy Ion Fusion Virtual National Laboratory Ion beam heating offers unique opportunities for HEDP science Advantages of Bragg-peak ion heating: Uniform heating of large volumes (few %)  aids diagnosis Volumetric energy deposition: no shocks, no x-ray or e - preheat Time scales long enough for equilibrium conditions Beam deposits ~75% of its energy; can measure beam changes High repetition rate valuable for setup, diagnostic tuning [ See L. R. Grisham, Phys. Plasmas 11, 5727 (2004). ] z 50  m Al foam 10% solid 3 mm dE/dX GSI: 40 GeV U, T e ~ 1kJ long cylindrical targets HIF-VNL: Bragg peak heating to maximize dE/dx & uniformity 24 MeV Na +, T e ~ few ~ 2.5 J foil targets, ~ 1 mm radius spot, ~ 1 ns pulse enabled by using metallic foam to minimize hydro motion Ion energy loss rate in targets

The Heavy Ion Fusion Virtual National Laboratory Innovations and a new approach are required to rapidly heat a small volume Beam Production Accel-decel / load-and fire injector Ion Transport via solenoids Acceleration via one of: - RF - DTL - Single-gap diode - Ionization-Front Accelerator - Pulse-Line Ion Accelerator Longitudinal Compression Neutralized drift compression Transverse Focusing Strong solenoid, Plasma lens, Two-stage focus, or Plasma channel pinch Workshop on Accelerator Driven High Energy Density Physics, LBNL, Oct. 26-9, 2004, brought together experts in targets, HEDP/WDM physics, accelerators: op/toc.html Solenoid confines the slowed, high line-charge beam Other approaches are possible Beam requirements

The Heavy Ion Fusion Virtual National Laboratory Beam requirements for 1 eV regime (NDCX-II) At InjectorBefore Compression At Final Focus (neutralized) Energy (MeV) 1.0 (  = 0.01)23.5 (  = 0.047) Pulse Duration  (ns) Pulse Length (m) Dimensionless Perveance K 1.8    Momentum Spread  p / p  2   7   Na + (A = 23), total charge = 0.1  C (6  ions) Normalized emittances:  nx = 2.3 mm-mrad,  nz = 33 mm-mrad Focus via 15 T solenoid; focal length ƒ = 70 cm Focal spot radius r spot = 1 mm ~  We are running a state-of-the-art hydro code, Hydra, to quantify beam req’ts J. J. Barnard, Poster LP1.80, 2:00 Wednesday; also PAC05

The Heavy Ion Fusion Virtual National Laboratory Gated Camera Neutralized Transport eXperiment (NTX) at LBNL was used to study neutralized focusing of high-perveance ion beams Neutralized Focusing

The Heavy Ion Fusion Virtual National Laboratory Non-neutralizedPlasma plug FWHM=6.6 mm FWHM=2.2 mm FWHM=1.5 mm % neutralized 6 mA Plasma density = 2 x /cm 3 Reduction of spot size using plasma plug and volume plasma was measured Plasma plug & volume plasma

The Heavy Ion Fusion Virtual National Laboratory 300 kV Marx Generator Ion Source Focusing Quadrupoles Diagnostics Tilt CoreNeutralized Drift Compression Section Vacuum Tank Neutralized Pulse Compression The Neutralized Drift Compression Experiment (NDCX-1a) uses an induction core to impart a velocity “tilt” to a section of the beam

The Heavy Ion Fusion Virtual National Laboratory Initial neutralized drift compression experiment (NDCX-1a) … 300 keV K + 25 mA Tilt-core waveform

The Heavy Ion Fusion Virtual National Laboratory ~ 50x longitudinal compression of neutralized beam was measured via phototube & Faraday cup, and simulated LSP simulation Faraday cup data Phototube data Phototube Time (ns) Compression ratio Time (ns)

The Heavy Ion Fusion Virtual National Laboratory Extended drift length (2-m) experiment demonstrates robust neutralized compression Greater sensitivity to neutralization Longitudinal beam temperature < 2 eV No evidence of two-stream degradation

The Heavy Ion Fusion Virtual National Laboratory LSP has guided NDCX experimentsEDPIC has clarified how beam motion through plasma generates waves Simulations help us understand beam flows in plasmas Kaganovich PAC05 BeamB Beam is injected with: 1.9-cm outer radius -22 mrad angle 0.05 mm-mrad emittance 0.21 eV T parallel Thoma PAC05, Sefkow PAC05

The Heavy Ion Fusion Virtual National Laboratory For HEDP studies, the accelerator, drift compression, and final focus must all work together Na + One concept: the beam … enters in Brillouin flow with a 5-10% velocity tilt … transitions to a Neutralized Drift Compression region … is focused by a strong solenoid … and by an assisted-pinch discharge channel, onto the target. Issues: Effectiveness of dipole trap at preventing plasma flow upstream Transition from Brillouin flow to neutralized transport Control of beam plasma instabilities and stripping in long plasma columns

The Heavy Ion Fusion Virtual National Laboratory Accelerator October workshop identified 5 approaches RF Linac, w/ or w/o stacking ring Staples, Sessler, Ostroumov, Chou, and Keller, PAC05 Ionization Front Accelerator Olson, WS Proceedings Drift-Tube Linac Faltens, WS Proceedings Pulse-Line Ion Accelerator (PLIA) Single-gap diode Olson, Ottinger, and Renk, WS Proceedings

The Heavy Ion Fusion Virtual National Laboratory 1 eV target heating >0.1  C of Na + 24 MeV Bragg peak 1 eV target heating >0.1  C of Na + 24 MeV Bragg peak Short Pulse Injector Short Pulse Injector Solenoid Focusing Solenoid Focusing PLIA Acceleration PLIA Acceleration Neutralized Compression Neutralized Compression Final Focus Final Focus A new accelerator concept (PLIA) can lead to a near-term HED facility (NDCX-II) with ten fold reduction in cost per MeV

The Heavy Ion Fusion Virtual National Laboratory PAC05: Briggs Henestroza Waldron Caporaso Nelson Roy Compact transformer coupling (5:1 step-up) Pulse Line Ion Accelerator (PLIA) is based on a distributed transmission line (helix) V s (t) from Pulse Forming Network An NDCX-2 Accelerator Cell Helical Winding in Epoxy Solenoid Cryostat Vacuum Pumping First low voltage bench test (R.J. Briggs, et al. - LBNL patent, 2004)

The Heavy Ion Fusion Virtual National Laboratory z(m) Longer beam is accelerated by “snowplow” (snapshots in lab frame) V (kV) E x (kV) z(m) V (kV) E x / 10 (kV) z(m) PLIA can be operated in a short pulse (“surfing”) mode or a long pulse (“snowplow”) mode Short beam “surfs” on traveling voltage pulse (snapshots in wave frame)

The Heavy Ion Fusion Virtual National Laboratory Particles Energy(MeV) Helix Voltage(MV) Current (A) HELIX ENTRANCE HELIX EXIT Z (m ) WARP3d simulation of NDCX-1d clarifies beam dynamics in the helix under the influence of space charge

The Heavy Ion Fusion Virtual National Laboratory Initial Pulse-Line Ion Accelerator tests are underway HV Cable Primary Turn Beam Direction Helix Winding Glass Tube Ground Return Outer Oil Vessel Support Structure

The Heavy Ion Fusion Virtual National Laboratory Input end Input Output end V(z) along the air-dielectric helix

The Heavy Ion Fusion Virtual National Laboratory High field solenoids Helix accelerating structure (in ‘snowplow’ mode) Matching solenoids Source (accel/decel) Beam species K + Total charge 0.1  C  nx  nz =(1mm-mrad) x (8mm-mrad) [ of NDCX-II design goal] We have designed a short pulse injector (NDCX-IC) which can serve as the front-end of NDCX-II

The Heavy Ion Fusion Virtual National Laboratory Decelerates the beam head Time ( s) Negative pulse accelerates tail more than head, giving tilt Main snowplow: shaped so that tail of pulse arrives at end of helix as beam end arrives there. This gives the beam an overall “tilt” in longitudinal phase space Voltage (MV) Strong longitudinal space charge effects in the snowplow can be controlled by shaping the voltage waveform

The Heavy Ion Fusion Virtual National Laboratory 3-D WARP calculations show how the design goals for the NDCX-II injector may be met

NDCX 1a,b,d experiments (next 2-3 years) can be done with existing equipment Inter- changeable HIF-VNL Plans Near-term plan centers on one facility with inter- changeable parts, to be used for several experiments quads NDCX-1c Load & Fire Injector NDCX-1d Pulse-Line Ion Accelerator (Helix) NDCX-1a Neutralized Drift Compression NDCX-1b Solenoid Transport Inter- changeable

The Heavy Ion Fusion Virtual National Laboratory x compression & solenoid transport (NDCX-1a,b) High- injector & PLIA w/ 0.1  C, 4 MeV (NDCX-1c,d) Integrated experiment w/ target heating to few eV (NDCX-2) A sequence of steps leads to an instrumented user facility Add chambers, targets, diagnostics NDCX-1c + ~ $5M hardware  > 0.1  C Na MeV Rep-rated (>10 Hz) system for studies of WDM at 1-10 eV (HEDP user facility)

Related papers at this meeting MONDAY (THIS SESSION) –S. Eylon, “Development of Fast Diagnostics for High Intensity Ion Beams,” BP1.83 –J. Coleman, “Low Voltage Beam Experiments on the PLIA,” BP1.84 –F. Bieniosek, “Diagnostic Development for Heavy-Ion Based HEDP and HIF Experiments,” BP1.89 –E. Henestroza, “Numerical Simulations of a Pulse Line Ion Accelerator,” BP1.98 –P. C. Efthimion, “Ferroelectric Plasma Source for Heavy Ion Beam Charge Neutralization,” BP1.101 –A. Sefkow, “A Fast Faraday Cup for Measuring Neutralized Drift Compression,” BP1.103 –E. A. Startsev, “Two-stream instability for a longitudinally-compressing charged particle beam,” BP1.104 WEDNESDAY –P. K. Roy, “Progress on neutralized drift compression experiment (NDCX-Ia) for high intensity ion beam,” KO1.15, Oral at ~12:18 PM –B. G. Logan, “Potential for Accelerator-Driven Fast Ignition,” KZ1.2, Oral at ~10:10 AM –J. J. Barnard, “Simulations of particle beam heating of foils for studies of warm dense matter,” LP1.80, Poster at 2:00 PM FRIDAY –E. Henestroza, “High Brightness Accelerator for Warm Dense Matter Studies,” UP1.16, Poster at 9:30 AM –D. R. Welch, “Longitudinal compression of an ion beam in the NDCX experiment,” UO1.10, Oral at ~11:18 AM

The Heavy Ion Fusion Virtual National Laboratory Related papers in Proc. PAC05 (IEEE/APS Particle Accelerator Conference), Knoxville, May 2005: A. Friedman, “Highly compressed ion beams for High Energy Density Science” …ROAB003/ROAB003.PDF R. J. Briggs, “Helical Pulseline Structures for Ion Acceleration” …ROAB005/ROAB005.PDF E. Henestroza, “Extraction and Compression of High Line Charge Density Ion Beams” …FPAT028/FPAT028.PDF W. Waldron, “High Voltage Operation of Helical Pulseline Structures for Ion Acceleration” …FPAT029/FPAT029.PDF G. Caporaso, “Dispersion Analysis of the Pulseline Accelerator” …FPAT034/FPAT034.PDF S. D. Nelson, “Electromagnetic Simulations of Helical Based Ion Acceleration Structures” …FPAT037/FPAT037.PDF P. Efthimion, “Ferroelectric plasma source for heavy ion beam charge neutralization” …TPAT036/TPAT036.PDF A. Sefkow, “A fast faraday cup for the neutralized drift compression experiment”…TPAT068/TPAT068.PDF F. Bieniosek, “Optical Faraday Cup for Heavy Ion Beams”…RPAT022/RPAT022.PDF J. Staples, “RF-Based Accelerators for HEDP Research”…RPAP023/RPAP023.PDF J. J. Barnard, “Accelerator and Ion Beam Tradeoffs for Studies of Warm Dense Matter” …RPAP039/RPAP039.PDF R. C. Davidson, “Multispecies Weibel and Two-Stream Instabilities for Intense Ion Beam Propagation Through Background Plasma” …FPAP026/FPAP026.PDF I. Kaganovich, “Ion Beam Pulse Interaction with Background Plasma in a Solenoidal Magnetic Field” …FPAP028/FPAP028.PDF P. K. Roy, “Initial Results on Neutralized Drift Compression Experiments (NDCX) for High Intensity Ion Beam” …FPAE071/FPAE071.PDF C. H. Thoma, “LSP Simulations of the Neutralized Drift Compression Experiment” …FPAE077/FPAE077.PDF

Backup

The Heavy Ion Fusion Virtual National Laboratory NDCX II design goals Beam species: Na A=23 Ion energy= 23.5 MeV (  =0.047) Final spot radius = 1 mm Final pulse duration < 1 ns Total charge in bunch = 0.1  C Emittances:  nx  nz < (2.3 mm mrad) x (33 mm-mrad) Target requirements dictate design goals of near-term HEDP accelerator (NDCX II) eV kT= Total charge (  C)  nx = normalized transverse emittance  nz = normalized longitudinal emittance f = focal length = 0.7 m for B=15 T, 23.5 MeV Na  = final bunch duration = 1 ns  = final ion velocity/ c Focal spot radius r spot depends on both transverse and longitudinal emittance