ARIES Documents -- Meetings ArchiveARIES Conference Call, 21 May 2002
Documented by L. Waganer
The next meeting date was confirmed as Monday, July 1, and the morning of Tuesday, July 2. GA will be the host and Ron Petzoldt is in charge of the meeting arrangements and visitor badging. The next conference call is 11 June at the usual time and the conference number will be 314-232-8169.
Ron Miller reminded the group that at the April 2002 project meeting Grant Logan suggested the recirculating coolant power for thick liquid wall option will introduce a sensitivity to the chamber size and repetition rate. Ron has been working on modeling this effect in the ASC model of the thick liquid wall chamber, ala HYLIFE-II.
Chamber Wall Engineering
Fluid modeling and experiments - Said Abdel-Khalik noted a question was raised at the April project meeting asking if the surface dried out after a drop was released from the surface. He has been investigating this effect. There is thinning of the film after the droplet release. He established the initial film thickness incrementally smaller until a point is reached where the final film thickness will go to zero and the porous structure surface would be exposed. The film thickness will be reestablished shortly by the liquid flowing from the porous structure and the recondensation of the vapor on the surface.
This leads to the second question. Can and how does the vapor recondense on the surface? He had been assuming an isothermal solution, but that is being modified to address recondensation.>
Another question was asked regarding the initial film condition. Said had input several surfaces (flat, sinusoidal, random) in his earlier modeling to represent the initial fluid conditions. He felt that after the shock, these conditions would encompass the expected range of initial conditions.
Beam Propagation - Simon Yu told the group that his group is preparing a point design beamline and beam transport for the thick liquid wall concept (HYLIFE-II). They are still trying to optimize the number of beamlines, but it is in excess of 100 beams. The spot size is around 2 mm as defined by Wayne Meierís driver code. They have found there are two causes of beam emittance growth.
Simon informed the group that Stephen Ness has joined LBNL to define a design window for a pinch mode beam transport at high chamber pressures. Don Hayes and Simon discussed the issue on the higher chamber pressures (40 torr?) might effect the behavior of the alphas (ion stopping) and the charge state of the xenon atmospheric gas. There was a factor of four in the effects seen by LBNL and UW. Simon and Don to resolve.
Craig Olson was questioning if the cold stopping power of the gas had been considered in the beam calculations. Simon said yes they had. The cold mass is included in the LBNL beam model.
Dave Rose and Dale Welch are investigating the magnetic field divertor to reduce charged particle density down the beamline. They are also analyzing the performance of a beam neutralizer (the plasma plug at the beam port exit).
Chamber Modeling - [Somebody] asked about the mean distance from the target (center of the chamber) to the thick wall inner surface. This is currently being parametrically treated as 0.5 m to 1.5 m although it is sometimes reduced to the range of 0.4 to 1.0 m radii. The question was asked to determine how the thick liquid layer reacts to the shock, assuming it is a solid layer. The response was that the thick layer is now being defined as a collection of closely packed individual circular jets surrounded by slab jets. This array is felt to be a better absorber of the gas impulse load, yet have the sufficient neutron stopping power. Jeff Latkowski mentioned that UC Berkeley has analyzed this phenomenon with partially published results. (See, as a starting point, Steven Pemberton, Thick-Liquid Protection in Inertial Fusion Power Plants, PhD thesis, UC Berkeley, May 2002.)
[Craig Olson?] said he had a definitive answer for Action Item #8, which is:
8. Determine driver (heavy ion beam) requirements for acceptable FLiBe vapor pressure, aerosol size and number density, and condensation film thickness in the beamline for different driver modes (C. Olson, S. Yu, and C. Debonnel)
[He?] stated that the stripping power will dominate and set the size of the aerosol and particles. The highest FLiBe vapor pressure would be 3 mtorr. The number density would be in the range of 5 x 1013 down to 5 x 1012 #/cm. Simon Yu mentioned that Don Olander's article contained the relationship between temperature and equilibrium vapor pressure. (See Olander, Fukuda, Baes, Fusion Science and Technology, March 2003.). The acceptable film thickness is still unknown and will mainly depend on the breakdown voltage of the contaminated surfaces.
RenČ Raffray said he is trying to gather data to help Don Haynes in the characterization of the FLiBe conditions within the chamber. He is working with Dai-Kai Sze to determine the decomposition parameters of FLiBe. Phil Shape said he also was working to establish the equilibrium parameters. He is improving by incorporating the FLiBe data and the correct chamber geometry. He will shortly be running his models. He is trying to bound the problem by using two limiting cases.
Chamber and Liquid Coolant Nuclear Analysis
Laila said she had no results to report as she is setting up her models for the thick liquid wall geometry.
Jeff Latkowski is comparing different shielding concepts and will downselect to the better one. He is also working on the magnet shielding over a range of number magnets. With the number of magnets increasing to larger numbers within the same cone angle, shielding the individual magnets becomes much more difficult. The design goal is to have the magnets life of plant, but as the shielding becomes thinner, it might be cost effective to change the magnets occasionally, which would also keep the WDR at lower levels.
Target Injection and Tracking
Ron Petzoldt is working on the action items to quantify the size and density of the FLiBe particles and vapor. He said the limiting size for the targets is around 0.29 mm and 2 mg/cc, but is working to refine that maximum limit. He noted that a density of 1 gm/m3 was limiting for the beam propagation.
Beam Magnets Design and Analysis
Simon Yu affirmed that his group is designing the beamline components, some of which Leslie Bromberg described in prior meetings. The peak magnetic field will be 8 Tesla, although there is work to try to lower that value to the range of 5-6 T. To lower the cost, the pulsed magnets are being considered. Both superconducting and normal magnets are being evaluated.
Draft of Thin Liquid Wall Report
RenČ Raffray offered a draft outline for the thin liquid wall report at the April ARIES meeting and Les Waganer enclosed the outline in the meeting min.utes. Please examine the outline and respond to RenČ if any changes are necessary. We should strive to quickly document this portion of our results so we can move on to the thick wall effort.