Cafe neutrino meeting minutes (03/01/10)
Present: E. Benedetto, F. Dufour, G. Prior, T. Stora, P. Valko, E. Wildner
Baseline 6He and 18Ne ion production for BB (T. Stora):
Next meeting: March 29th room 6-2-004 at 10:30 am
Numbers quoted on slide 2 (.pdf) are from the final report, whereas previous slides or documents are giving 2 (.2) 1013 for both ions. From calculation done by Elena W. group, the number from Thierry are too big but this is not taking into account losses in the source. Numbers given here are the numbers of the neutral ions coming from the target and entering the ECR. Final report is published. CERN is investigating a different alternative for the low-energy injection. Two different manners exist to produce the ions. One uses a heavy ion beam on target, then a fragmentation technique for isotope separation such as FAIR. The other one called ISOL (Isotope Separation On Line) uses a primary beam of few MeV/u on target. A good fraction of the energy is deposited in the target. Current values quoted on slide 3 are the maximum extracted current at the different locations. Losses have to be carefully estimated such as release loss, condensation...and most of it is driven by engineering. Slide 4 gives the formula for the intensity for one ion specie with a given state of charge. Need to compute the numbers. Loss by diffusion stands for the diffusion time to get out of the target for a given ions with a finite lifetime. Loss by effusion stands for evaporation once extracted from the target. Ionization efficiency is defined by parameters inherent to the ion properties. Lot of developments and limitations are constrained by these efficiency numbers. Have to rely ultimately on results from experiments that will have to be performed.
For 6He consider a primary driver close to EURISOL baseline. Send the proton beam to a neutron converter (this is a neutron-rich material such as tungsten). Will produce 1014 6He/s. Experiment was made at CERN to check these numbers. Article in preparation. Used for the neutron converter BeO. This is a thiner target (10% reduced scale compared to the one that will be used for BB). Trise (slide 6) characterizes how fast 6He is evaporated from the target to reach the ion source. In first approximation need to multiply by a factor 10 to get the final amount of ions you can release. Spallation targets use GeV proton on the same type of neutron converter. Some installations operate at 100 kW and show that neutron converters can be used without too much problems. Seems that for 6He the number quoted on slide 1 can be delivered.
For 18Ne this seems more difficult. From the simulation used not enough (1012) 18Ne is produced with 1 GeV proton at 100kW. Also 100kW on these targets is a problem. Need to remove the heat without increasing the extraction losses. At least one order less than what is required. Marc Loiselet used at LLN 3He in 16O(3He,a)18Ne reaction. This almosts fully stops order of MW of beam. A 86 cm diameter target can be used, evacuating the heat on the backside. But extraction losses need to be carefully estimated. For ITER, people starts thinking about MW order. From linac point of view maybe difficult to achieve. Thierry approach is to use again a proton beam on target but trying to avoid entering the MW region. 18F already used for PET imaging. May be able to use an intermediate energy (70 MeV) proton on 19F, 24Mg or 27Al. In the range 100 kW to 1 MW solid targets are not anymore possible. A liquid target can be operated using a melted metal loop. Starting to investigate that. Problem is to find how much power is needed to produce the 18Ne. Code used at the time of the meeting in Grenoble does not have the proper physics in. IAEA report gives cross-section computed using with a different code and the numbers are more optimistics here with NaF. Advantage is that this was investigated for Nuclear Industry. Seems that 2 1013 18Ne/s could be produced. Would need to dissipate abour 400 kW which can probably be handled. Few experimental data are available on 18F that can be used to benchmark the code. Peter Valko is coming at CERN for 6 months and will work on cross-checking the simulation code and calculation that Thierry has done. In term of machine, 2 mA 70 MeV proton cyclotron do exist. Maybe a linac can be used instead, this is an easy technology. Commercial cyclotron do exist but maybe not 10 mA. Will need to look into that. Oakridge and PSI have both 70 MeV protons available but no manpower nor resources available for the time being to make an experiment that would help cross check the simulation results for NaF. Depending on what machine is needed will drive the cost of the BB. First estimate will be done assuming Linac4. Peter V. work will help understand if another type of machine would have to be used.
In order to separate the isotopes, selectivity can be done at first using a coal line. Then chemical selection is performed using a mass spectrometer in the ISOL case. For 8B it BF molecule should be used. If breaking the molecule before the ECR, some contamination will come from 8Li which is very difficult to seperate from 8B whereas Li does not combine with F. Also 16O can come as 16O2+. Same problem with 8Li. Now realizing that for 18Ne will also need to work out the separation as 18O2+ this time is a contamination source.
Costing workshop at CERN, not everyone received the email with the indico web page: http://indico.cern.ch/conferenceDisplay.py?confId=85004.
Elena W. would like to hear about the status of EUROnu WP3 work. Michel and Gersende will prepare an update for after the IDS-NF meeting.