beams08

Acceleration of Macroscopic Particle to Hypervelocity by High Intensity Beams Yian Lei, Jian Liu School of Physics, Beijing Univ., China Beams 08, Xian Contents     Hypervelocity, definition and applications Impact Fusion Macroscopic particle (macron) acceleration High intensity beam macron acceleration concept  Dynamic compensation ”blowing-pipe” design of a macron accelerator  Physics and challenges Hypervelocity  Common definition: macro objects, 3000 km/s and above  Research fields: space exploration, micrometeorites collisions, weapons  Definition here: macroscopic objects, less than 1 gram, 200-1000 km/s  Application: high energy density physics (HEDP) studies, impact fusion Hypervelocity impact in HEDP  vs. other methods, laser, electron or ion beams, anvil  Higher energy density (pressure), ~Gbar  Better energy deposition, no high energy electrons, less radiation.  A workbench for HEDP  J. Liu, Y. Lei, HIF 2008, Aug., Tokyo Impact Fusion Concept  Macron @ 200~1000 km/s, shots into liquid or solid DT. Winterberg, 1964  Historical events, Impact workshop @ LANL, 1979, LANL evaluation 1980  Rejected because people believe the macron size should be around 1 gram and kinetic energy 10~50 MJ for impact ignition, and there is no way to accelerate such a macron to the speed  For electrostatic accelerators (linear rf synchrotrons), the length is over 10000 kilometers New Idea of Impact Fusion New Idea of Impact Fusion  Bullet: millimeter (milligram) size diamond, (vs gram size metallic ones, shorten accelerator length by 10 times)  Target: crystal DT methane (CD2T2), (vs liquid or solid DT), higher DT concentration, higher fusion α particle stopping  Mechanism: particle mixing and thermolization, (vs shock wave or global compression)  Ignition energy is 1~2 MJ (another 10 times)  Linear RF accelerator length: ~100 km Advantages  “Stand-off”, no close contact components (to fusion spot)  No precompression, no precise positioning  High Q, unlimited and easy tailored output energy, propagating fusion burn.  Accelerator: no emittance, no magnets, slow bullet, low vacuum, high efficiency  High inject energy efficiency, 70% bullet energy goes to DT ions, vs 10+% in laser, HIF, Z-pinch  Close energy and neutron harvesting (tritium & 3He breeding, high intensity neutron source)  Lei, et al, IAEA FEC2008, Oct. Geneva  Low cross section, microbarn ~ barn best candidate: D + T = 4He + n, 5 barn at ~ 100keV  Low luminosity: ~ 1030 cm-2s-1 D shooting liquid T, ~ 1037 cm-2s-1  Low energy density ion current ~mA, 1016 s-1, if reaction area 1mm2x1m, ring 100m, fusion energy: 1016x1016x5x10-28/10-6 /100x18MeV ~ 1.5x10-4W  Low accelerator efficiency Some facts      D(T,n)a cross section > 1b, if E > 50 KeV Other 1 ~ 50 mb, E > 100 KeV 50 keV ~ 5x109 K Tokamaks 1~10 keV Modern particle accelerators: • Large Hadron Collider (LHC), 7TeV • International Linear Collider (ILC) 500~1000GeV, • SLAC 50GeV  1TeV/100keV = 107 How about macroscopic collision?  1ug LiD(T) ~ 6x1016 LiD(T) pairs ~ 6x1017nucleons ~ 2.4 x 1017 electrons  Knock out (or put upon) 6x1010 electrons, that’s 10-8 Coulomb. If charge is evenly distributed, static electric energy ~ 5 x10-3 J, which is less than it’s total chemical bond energy (10-2J)  A 1TeV accelerator can put 100keV energy to each nucleon, means D 200keV, T, 300keV, Li-6, 600keV, Li-7, 700 keV. Total enery: 6x1010 x 1TeV ~ 10kJ, speed ~ 4500km/s Lithium hydride  LiH is a colourless crystalline solid, although commercial samples appear gray. Characteristic of a salt-like hydride, it has a high melting point (689 ° C or 1272 °F). Its density is 780 kilograms per cubic metre. It has a standard heat capacity of 29.73 J/mol*k with thermal conductivity that varies with composition and pressure (from at least 10 to 5 W/m*K at 400 ºK) and decreases with temperature. -----Cited from wikipedia.org Shooting it to a stationary target…  Also a LiD(T) rod, 10mmx10mmx100mm  Facts:  D(T) pass through each other about 107 times, fusion almost surely happen, that’s ~ 2mm  luminosity ~ 1050 cm-2s-1  Temperature: 500keV at beginning, then goes down  Time of reaction: ~0.2us. Laser ICF: 0.07(8)us  Other fusion process can occur: D-6Li, D-7Li, mostly DT. Inertial confinement?  Scattering cross section is larger than DT reaction cross section (10~50 barns). Quasiequlibrization process.  Mean free path: ~0.2 mm  Preliminary simulations show 5~30% of the bullet D(T) quantity fuse. Considering the target, the fusion rate is very low. But energy produced is much larger than the incoming bullet. Chain-action like effects  The fusion products (high energy alpha particle, neutron) can pass a decent part of its energy to other nuclei. Cross section: alpha particle: 10~50 barn, neutron, ~1 barn  Those nuclei can join fusion process Energy gain  If we manage (by bullet design, a bunch of bullets, two way impact, etc), and make 1mg DT fuse in each shot, the fusion energy gain is equivalent to that of burning 10Kg coal.  If this can happen every second, it can power a 140MW plant. Accelerator issues  Power consumption: • Linear Accelerators (500GeV~1000GeV) 100~300MW • LHC, 7 TeV, 120MW  We may have to use linear ones, for the mass/charge ratio of the bullet is too high.  The speed of the bullet is much less than c. Good or bad? May need special design of accelerator. What’s new here?  Slightly charged (?), chemically bound, macroscopic bullets provide much higher luminosity, plasma density, and energy density, which are vital for fusion processes. What misses here? (Loopholes)  Can’t charge macroscopic particle to that much of electricity (10-7 of it’s molecule number), this charge is actually quite high, imperfection of the material will cause break-ups.  Charged bullet disintegrates during acceleration. Resonance, heating, uneven charge distribution.  Simulation is wrong, not that much fusion happen, energy gain is too small. Most probably the bullet (main reaction area) cools off sooner. Comfortable facts  Laser driven Inertial confined fusion put 1~2 MJ energy into a D-T target, 15-30% of the total energy goes to heating and compressing the ablated core, confined time < 0.1us  Some other efforts to increase the shooting energy, bullet size, confine time are possible.  Electricity-microwave conversion efficiency is very high. Meter-wave. Advantages  Fusion products go forward. Reaction/energy collection chamber can be very large, reducing wall damage. (vs. Tokamaks)  Can easily work continuously (vs. Laser ICF)  If the size of the target increases, chain-action like effects could happen, free energy gain.  Easy to control  Easy to model  Easy to prove or falsify (SLAC can try a smaller shot than quoted here) Some concerns  Charging bullet, bullet design, ballooning, metal coating, not necessarily to be LiD(T)  Radio frequency of the accelerator, low heating rate  Bullet speed is good, much shorter linear accelerator than particle ones, 1TeV ~ 10km  First goal, build a primary accelerator, nanogram particle to 1~10km/s. Should be easy, no vacuum, no cooling, no magnets, basic electrical & mechanic work.