1 / 11

First application of ranging-out method and hybrid 3Hen counter at ISAC-1:

3Hen at TRIUMF. K. P. Rykaczewski. First application of ranging-out method and hybrid 3Hen counter at ISAC-1: measurement of absolute beta-delayed neutron rates (I β n ) for Ga and Ge isotopes around N=50. collaboration of ORNL Physics - TRIUMF - Guelph - Simon Frasier

galeno
Télécharger la présentation

First application of ranging-out method and hybrid 3Hen counter at ISAC-1:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 3Hen at TRIUMF K. P. Rykaczewski First application of ranging-out method and hybrid 3Hen counter at ISAC-1: measurement of absolute beta-delayed neutron rates (Iβn) for Ga and Ge isotopes around N=50 collaboration of ORNL Physics - TRIUMF - Guelph - Simon Frasier UTK - ORAU - ORNL Reactor Science LSU - Mississippi - Warsaw Verification the absolute βn branching ratios Iβn for N=48 79Ga, N=49 80Ga, N=50 81Ga, and measure for the first time Iβn value for N=51 83Ge. Proposed experiment represents a step towards the understanding and improving of ISAC discovery potential for decay studies of new nuclei produced in fission. (before the high resolution mass separator will be operating at TRIUMF).

  2. Br88 Br87 Br89 Br91 Br92 Br85 Br90 Br93 Br94 Br86 Br81 Br83 Br84 Br82 31.80 m 70 ms 16.36 s 55.1 s 4.40 s 2.40 h 2.90 m 541 ms 343 ms 152 ms 35.28 h 55.65 s 1.91 s Se91 Se89 Se85 Se88 Se83 Se84 Se90 Se81 Se82 Se86 Se87 Se80 22.3 m 3.3 m 410 ms 1.53 s 5.50 s 32.9 s 18.45 m 270 ms 14.3 s As84 As82 As83 As86 As79 As80 As81 As85 As87 13.4 s 19.1 s 33.3 s 4.2 s 480 ms 15.2 s 9.01 m 2.02 s 861 ms 484 ms HRIBF β--n-TAS-En results marked in red Ge83 Ge86 Ge85 Ge82 Ge81 Ge79 Ge78 Ge84 Ge80 ?bn 0.1% 1.85 s 7.6 s 18.98 s 946 ms 230 ms 4.55 s 494 ms 221 ms 29.5 s 88 m Ga86 Ga83 Ga81 Ga77 Ga82 Ga84 Ga85 Ga78 Ga79 Ga80 bn 12% bn 0.9% bn 0.09% 93 ms ~40 ms 1.68 s 2.84 s 5.09 s 85 ms 1.21 s 599 ms 308 ms 13 s Zn82 Zn83 Zn79 Zn77 Zn81 Zn80 Zn76 Zn78 5.7 s 304 ms 995 ms 2.08 s 537 ms 117 ms 1.47 s 228 ms Cu80 Cu79 Cu78 Cu77 Cu75 Cu76 1.22 s 637 ms 290 ms 170 ms 338 ms 481 ms Ni74 Ni78 Ni76 Ni77 Ni75 βn branching ratios around N=50, for 79Ga,80Ga,81Ga and 83Ge precursors, to be measured at TRIUMF-ISAC 28 0.9 s 110 ms 344 ms 238 ms 128 ms 50

  3. Decay studies with post-accelerated fission products C.J.Gross et al., EPJ A25,115,2005 76Cu Range out exp gas cell spectra no 76Zn !!! Energy loss 76Ga 76Ge Total ion energy Laser ion source at TRIUMF IRIS-1 Mass separator M/ΔM ~ 1000 fission fragments ~1011/s HRIBF charge exchange cell ~ 5% efficiency Positive ions 6 g 25 g 238U ORIC : 54 MeV protons 12- 18 mA +/-40 keV +/-160 keV TRIUMF 500 MeV ~ 10  A Tandem accelerator (negative ions only) ~ 10% efficiency ISAC ~ 0.1 % overall efficiency beam kicker eb ~70% en ~44% eg~4% HRIBF ~ 0.5 % overall efficiency Isobar separator M/DM ~ 10000 gas cell Range out experiment 2-3 MeV/u

  4. Why the decay spectroscopy of fission products is difficult at ISAC ? • beams of interesting ions come with usually much stronger contamination • of higher-Z fission products (this problem is not ISAC specific). • But here the selective laser ion source combined with ranging-out technique can help to purify Ga and Ge ion beams. • ISAC post-acceleration scheme requiring a Charge State Booster creates • a lot of stable ion contamination in the post-accelerated beams (see proposal). • But these are stable contaminants – no radiation emitted ! • Higher-Z contaminants should be stopped in our Ionization Chamber. Unfortunately, the combination of selective ionization, ranging-out and radiation detection is not (yet) an universal solution to the beam contamination problem – every effort to characterize and reduce the beam contamination at TRIUMF is extremely important But this experiment can help to advance beam purification techniques at ISAC

  5. Ranging-outof higher-Z components, counting and transmitting Ga ions, deposition on Ed Zganjar’s MTC followed by a transport and β-n- detection 3He tubes 3He tubes This experimental setup is able to remove the radioactive isobaric contaminants. However, stable ions can overload the ionization chamber (tested up to 300 kHz ion rate) making the event-by-event identification and detection difficult to impossible. The proposed solution: we reduce the beam intensity to the limit of, e.g., 81Ga detection in the IC and βn setup (factor 1000). We measure the absolute rate of 81Ga ions vs the β rate and optimize the gas pressure. Later we use the IC in a passive degrader mode and obtain the rate of implanted 81Ga ions from β counts. MCP can count reliably up to 106 pps, but it counts full ion beam intensity before IC.

  6. 76Ge 76Ge 250 kHz 76Se 150 kHz 76Se 76Ge 76Ge 225 kHz 300 kHz 76Se 76Se The advantages of a small transmission ion chamber • Short cathode to anode distance (~3 cm) • drift time minimized over 1.5 cm of beam-anode distance • CF4 gas • a fast gas (drift time ~100 ns/cm) • Total path length in gas (~7 cm) • compact to minimize beam blow up • Segmented anode (6 electrically separated) • measured energy loss dependent on total energy • a measure of range (cm scale) • different combinations of anodes can select and isolate events of interest • Small windows with metal support wires • mylar windows of 0.9 μm and 2.4 μm • 0.9 μm withstands excess of 200 Torr • modular design • easy to replace window quickly • openings 16 mm diameter • Recent addition (untested) • central wire “guard ring” to smooth electric field gradient near window to improve anode 1 & 6 performance

  7. 79Ga+12 Background current observed from the CSB during 2011 development runs. The vertical lines show the transmitted region that corresponds to the A/q for 79Ga12+. The 46Ti7+, 79Br12+, 86Kr12+, 92Mo14+, 131Xe20+, and 132Xe20+ ions are responsible for this current. Worst case scenario: 100 pA of 46Ti7+ means 9•107 ions/s. With factor 103 down (slits closed), we have 104 -105 pps in IC. 79 Projected acceptance of the ISAC-I RFQ. The region labeled “B” maximizes A=79 transmission, and reduces possible 86Kr and 131Xe by an order of magnitude. Fine-tuning of the phase of the RFQ, depending on the exact stable-beam composition, can significantly reduce the background.

  8. The proposed experiment represents an ideal commissioning experiment for the Charge State Booster, especially when considering that we can give instantaneous online feedback of the beam composition, and provided that the stable-beam rates are not in excess of ~ 109 pps the measurement can be successful. The presented project has an obvious continuation path towards new exotic beta-delayed neutron emitters, like 86Ga and even 87Ga, after demonstrating successful study of activities produced at higher rates. (let’s keep 3Hen at TRIUMF, if we can get new results there)

  9. Beam time accepted: Iβn for 79Ga, 80Ga and 81Ga, for each ion: one 8-hour shift of tuning plus one 8-hour shift for measurement amount to four 12-hours shifts 85Ga rate(towards new nuclei): two 12-hour shifts Iβn for 83Ge: one 8-hour shift tuning plus six 8-hour shifts for measurement amount to about five 12-hour shifts Total of eleven 12-hour shifts K. Rykaczewski, TRIUMF, 12th July 2012

  10. Detectors for beta decay studies 3Hen array after “ranging-out” εn~80% εn~44% Ed Zganjar mounting 3Hen array at LeRIBSS hybrid 3Hen-β- array at LeRIBSS K. Rykaczewski, TRIUMF, 12th July 2012

More Related