Present status of SISAK and future plans

Transcription

1 Present status of SISAK and future plans Presented at 2 nd SHE Collaboration Meeting by Jon Petter Omtvedt Shinshu University, Nagano, 23 rd September 2011 Outline 1) What is SISAK? 1) Principle 2) History and highlights 2) SISAK SHE research a. Adoption to SHE research b. Highlights c. Experience gained 3) The SISAK future... a. Strengths and capabilities b. Requirements c. Oslo Cyclotron Laboratory 4) Conclusions Slide 2 SISAK Oslo Group and Collaborators Project leader: Prof. Jon Petter Omtvedt Senior scientists: Prof. Jorolf Alstad and Prof. Tor Bjørnstad. Post docs: Dr. Karsten Opel, Dr. Alexey Sabelnikov, Dr. Nalinava Sen Gupta. PhDs: Marcus Johansson (2000), Liv Stavsetra (2005), Li Zheng (2007), Fereshteh Samadani (2010), Darina Polakova (on-going). Masters: Kristin Fure (1998), Liv Stavsetra (1999), Elin A. Hult (1999), Jan-Erik Dyve (2000), Hanne Breivik (2001), Fereshteh Samadani (2006), Beyene G. Haile (2008), Frøydis Schulz (2009), Johannes Nilsen (2009). Key collaborators: Prof. Darleane Hoffman (LBNL), Dr. Ken Gregorich (LBNL), Prof. Heino Nitsche (LBNL), Dr. Matthias Schädel (GSI), Prof. Christoph Düllmann (GSI), Prof. Gunnar Skarnemark (Chalmers), Dr. Klaus Eberhardt (U. Mainz), Dr. Norbert Trautmann (U. Mainz), Prof. Andreas Türler (PSI), Dr. Alexander Yakushev (GSI). Many others: Students, technicians and other personnel at Oslo, LBNL, Mainz and GSI. Part 1) What is SISAK? a. Principle b. History and highlights Slide 3 Liquid-liquid Extraction System SISAK SISAK = Short-lived Isotopes Studied by the AKUFVEtechnique AKUFVE is a Swedish acronym for an arrangement for continuous investigations of distribution ratios in liquid-liquid extraction. Slide 5 Slide 6 1

2 Inlet/outlets Separation chamber Rotating cup Special centrifuges Phase boundary Special centrifuges Slide 7 Slide 8 Throttles control phase separation Phase separation monitored by measuring light transmission Slide 9 Slide 10 Centrifuge (H-10) developed in Gothenburg in the 1970s. Application and further development by a Gothenburg- Oslo-Mainz collaboration. Separation chamber volume reduced with each generation: ml 12 ml 0.3 ml Reinhardt & Rydberg, JActaChemScand 23 (1969) p2773. Persson et al. RCA48, (1989) p177. Commercialized by Swedish company MEAB AB. Special centrifuges Three generations Designed in 1970s Slide 11 Standard setup with degasser and main extraction stage Omtvedt et al., J. Alloys & Comp (1998) p303. Special centrifuges Three generations 0.3 ml chamber PEEK Two types: liquid-liquid gas-liquid Slide 12 2

3 History (I) Project initiated in 1969/70 by Janne Rydberg at Chalmers to see if the new H-33 centrifuges could be used to study shortlived chemical states. Soon it was realised that the system was suitable for studying short-lived nuclei. In 1971 the first on-line n-irradiation, separation and γ- measurement was performed on Cu nuclei. The name SISAK was adopted in 1972 (Short-lived Isotopes Studied by the AKUFVE technique). September 1972 SISAK moves to Oslo, which has a n- generator yielding 10x more neutrons (La, Ce and Pr nuclei are investigated). History (II) In 1974 a successful test is performed in Mainz. It s the first time a gas-jet has been successfully coupled to a chemical system. In 1975 the Göteborg-Mainz-Oslo collaboration is formed. In 1975 a new and much faster centrifuge is developed and tested, the H-10 ( SISAK 2"). In many successful experiments (La, and Ce) in Mainz are performed. Parallel to this a huge effort is done to develop chemical separation systems for Br, I, As, Tc, Ru and Pd. Experiments on Tc isotopes are started in In 1981 a new degasser is developed, which results in faster transport and less radiation health-hazards. First experiment at GSI in 1985 (on 243,244 Np). Slide 13 Slide 14 History (III) First experiment at GSI in 1985 (on 243,244 Np). In 1987 it is decided that SISAK will be used for transactinide research. This demands that the waste volumes must be reduced. New and smaller centrifuges ( SISAK 3") are developed and built in : SISAK 3 is used to study e.g. the 0.8-s 110 Tc and 0.8-s 113 Ru. In 1994 the 0.30 s nuclei 111 Tc was observed with SISAK. It s the most short lived nuclei ever observed after separation with an aqueous based system. Part 2) SISAK Outline SHE research a. Adoption to SHE research b. Highlights c. Experience gained Slide 15 History SISAK and SHE In chemical separations systems for Rf, Db and Sg are developed. Model experiments are done at GSI and PSI with the homologes Hf, Ta and W and in Mainz with Zr, Nb and Mo. In parallel, a α-detection system is developed, based on liquid scintillation counting techniques. In 1995 the first SISAK experiment at LBNL is performed. However, the experiments fails to detect Rf and Db. In further transactinide experiments are done at GSI (Sg), LBNL (Db) and PSI (Rf). Regretfully no transactinide activity is observed due to huge background and pile-up problems. Slide 17 Early SISAK Oslo-group Jorolf Alstad, Liv Stavsetra, Kristin Fure, Elin A. Hult, Marcus Johansson, Jon Petter Omtvedt in collaboration with Mainz and Goethenburg groups Slide 18 3

4 Counts/channel Counts Basic SISAK System late 1990s Centrifuge Power Supply (Spintec Sf750) On-line Liquid Scintillation α-detection Light guide Orgainc phase reservoir Centrifuge Power Supply (flow: ml/s) (Spintec Sf750) Gas jet L/min Pump Phase Purity sensor Mixer Org. Aq. Degasser Main Phase Purity Extraction sensor Pump Phase Purity monitor Amplifier (PC with 0-5V Aqueous analog inputs) phase reservoir (flow: ml/s) Pump Power Supplies (0-35 V, 1 A / pump) Outlet Inlet Rn, 6.82 MeV MeV Scintillation chamber 215 Po, 7.39 MeV PMT Wierczinski et al., NIM A 370 (1996) p532. Wierczinski et al., Radioan. Nucl. Ch. 247 (2001) p57. Stavsetra & Omtvedt, Radiocarbon (2002) p24. Slide 19 Channel Slide 20 Pulse-Shape Discrimination (PSD) PSD spectrum Slide 21 Slide 22 Post extraction addition of Scintillator A Magic Trick is Needed Adding the scintillator ingredients after the extraction stage greatly improved phase separation A Small changes in phase purity causes large changes B in quenching A centrifuge degasser was also added to enable Ar flushing to remove O 2. The degasser also helps pump the liquid through the detectors, hence it s refered to as a booster Channel Energy (MeV) Slide 23 Slide 24 4

5 Daughter energy (MeV) Counts On-line Quench Correction Magic Trick Works! A Channel B Energy (MeV) Stavsetra, Hult & Omtvedt, NIM A 551 (2005) p323. Stavsetra et al., NIM A 543, (2005) p509. Slide 25 Slide 26 But it does not work for SHEs Preseparation w. RTC 9,0 8,8 8,6 8,4 8,2 8,0 7,8 7,6 7,4 Reaction: 249 Cf( 12 C,4n) 257 Rf Decay: 257 Rf (4 s) 253 No (1.7m) 8,0 8,5 9,0 9,5 10,0 Mother energy (MeV) Berkeley Gas-filled Seperator (BGS) Developed at LBNL by Kirback & Gregorich. Kirback et al., NIM A 484 (2002) p587. Omtvedt et al., J. Nucl. RadioSci. 3 (2002) p121. Preseparations removes unwanted background. Recoil Transfer Chamber (RTC). Allows chemical experiment to focus on chemical properties, not separation. Makes α liquidscintillation detection possible. Slide 27 Slide 28 Preseparation w. RTC RTC windows New RTC: 100 x 40 mm window supported on a honeycomb grid with 80% transmission. Old RTC: 57 x 143 mm window with 80% transmission honeycomb. Slide 29 Slide 30 5

6 Proof of Principle Proof of Principle 208 Pb( 50 Ti,1n) 257 Rf 6 μm mylar window in RTC. No chemical separation. Gas-jet dissolved directly in LS solution. Detecting 257 Rf- 253 No correlations. Slide 31 Slide 32 Proof of Principle SHE Chemistry Rf extracted as a DBP complex from 6 M HNO 3 solution with HDBP in Toluene. Rf extracted with TOA from oxalic acid. Rf extracted with TOA from sulphuric acid. Stavsetra et al., NIM A 543, (2005) p509. Slide 33 Slide 34 Oxalic Acid LBNL 2000: BGS - SISAK - LS-array 0.1 M Oxalic acid. Rf is extracted as oxalate with tri-n-octylamine (TOA, 0.1 M) into toluene. This system do not need a washing step (as do the nitric- acid system). Reaction: 208 Pb(237 MeV 50 Ti 12+, 1n) 257 Rf performed at LBNL using the BGS with RTC. Measured ~70% extraction for Rf, comparable to Hf. Slide 35 6

7 Aq.phase Extraction from Sulphuric Acid Rf Extracted with TOA from Sulphuric Acid In a work by Yagodin et al.[1] it is shown that Zr is preferentially extracted (with respect to Hf) by tri- octylamine (TOA) from sulphate solutions. Results can be obtained at modest sulphate and TOA concentrations. Two experiments, in 2003 and 2005 (to be published) experiment with double detector arrays in order to measure activity in both phases simultaneously. [1] G.A.Yagodin et al. Proc. Int. Solv. Extraction Conf (ISEC71), the Hague, April 1971, paper 208. Results from LBNL 2003 & 2005 SISAK experiments Main result Rf seems to behave more like Hf than Zr when complexed with sulphate ligands. This is in accordance with theoretical expectations (Pershina et al. RCA 2007). Slide 37 Slide 38 Full SISAK system for SHE LBNL 2005: SISAK + 2 Detector Arrays Gas jet Org. phase Scintillator Org. phase Ar flushing To detectors (organic phase) Aq. phase Degasser Main Extraction Org. phase Aq.phase Extraction Scintillator Added in 2005 Ar flushing To detectors (aqueous phase) Slide 39 Slide 40 SISAK achievements Achievements Important Improvements The transactinide 257 Rf detected with SISAK liquid scintillation detectors, proved that studying SHE with SISAK is possible Only one throttle Rf extracted from 6 HNO 3 into toluene with HDBP, first SISAK chemistry experiment on a SHE. - Rf extracted from oxalic acid into toluene with TOA Rf extracted from sulphuric acid into toluene with TOA Rf extracted from H 2 SO 4, simultaneous detection of both phases enhances yield and precision Knowledge from BGS-RTC used in building two RTC s for TASCA, one large and one small New small RTC built for BGS Db detected with SISAK LS-detection system First GSI experiment with SISAK@TASCA, testing Hs-chemistry with Os. Org. feed Premixer 0.7 mm (i.d.) tubes 2005 Slide 41 Slide 42 7

8 Hassium Equilibrium Extraction Reaction: HsO 4 + 2OH - [HsO 4 (OH) 2 ] 2- Assumptions: OsO 4 is primarily dissolved in organic phase. [OsO 4 (OH) 2 ] 2- primarily dissolved in aqueous phase. Experiment performed by von Zweidorf et al., but could not distinguish between Os and Hs behaviour. von Zweidorf et al.: Radiochim. Acta 92, 855 (2004). Slide 43 Samadani, PhD thesis Univ. Oslo (2010). Samadani et al., RCA 98 (2010) p757. Samadani et al., to be submitted to RCA. System for investigating Hs Developed with γ-emitting Os (OCL) and α-emitting Os (GSI). Slide 44 Equilibrium condition Premixer Part 3) The SISAK future... Extraction of OsO 4 into toluene, from Samadani et al., RCA98 (2010) (DOI /ract ) Phases must be mixed thoroughly enough to ensure extraction under equilibrium conditions. Slow kinetics will lead to severe decay loss. Efficient mixing very important! Slide 45 a. Strengths and capabilities b. Requirements c. Oslo Cyclotron Laboratory The Future? How Heavy SHE can SISAK handle? Good chemistry cases: - Take full advantage of the freedom offered by preseparation. - Must be interesting for theoreticians. - Must be clearly understood (equations known). - Fast kinetics. Reliability and ease of operation: - Less maintenance and fewer break-downs. - Replace degassers with membrane separation units. Logistics and man-power: - Need collaboration with an accelerator lab with a local SISAK group/students or at least liquid-phase chemistry group. SHE experiments with rutherfordium not regarded as particularly difficult anymore. SISAK has only done chemistry experiments with rutherfordium. Normal experiments uses 1-min 261 Rf, SISAK used 4-s 257 Rf... No other liquid phase chemistry has tackled 4-s SHE. For SISAK, the difference between Rf, Db, Sg, Bh and Hs is about crosssection and decay pattern, not half life. Slide 47 Slide 48 8

9 Oslo Cyclotron Laboratory (OCL) Conclusions Scanditronix SC35 cyclotron OCL is set-up with target chamber and gas-jet to supply adjacent chemical laboratory with a wide selection of SHE homologues for model development and tests. SISAN ability to measure 4-s 257 Rf proven in many experiments and for three different chemistries. Likely that SISAK can also handle Db and Sg without problem. SISAK chemistry to study Hs developed. SISAK detector system very effective and true on-line can be used for other liquid-phase experiments. Slide 49 Slide 50 SISAK Oslo Group and Collaborators Project leader: Prof. Jon Petter Omtvedt Senior scientists: Prof. Jorolf Alstad and Prof. Tor Bjørnstad. Post docs: Dr. Karsten Opel, Dr. Alexey Sabelnikov, Dr. Nalinava Sen Gupta. PhDs: Marcus Johansson (2000), Liv Stavsetra (2005), Li Zheng (2007), Fereshteh Samadani (2010), Darina Polakova (on-going). Masters: Kristin Fure (1998), Liv Stavsetra (1999), Elin A. Hult (1999), Jan-Erik Dyve (2000), Hanne Breivik (2001), Fereshteh Samadani (2006), Beyene G. Haile (2008), Frøydis Schulz (2009), Johannes Nilsen (2009). Key collaborators: Prof. Darleane Hoffman (LBNL), Dr. Ken Gregorich (LBNL), Prof. Heino Nitsche (LBNL), Dr. Matthias Schädel (GSI), Prof. Christoph Düllmann (GSI), Prof. Gunnar Skarnemark (Chalmers), Dr. Klaus Eberhardt (U. Mainz), Dr. Norbert Trautmann (U. Mainz), Prof. Andreas Türler (PSI), Dr. Alexander Yakushev (GSI). Many others: Students, technicians and other personnel at Oslo, LBNL, Mainz and GSI. ANNOUNCEMENT: Post. Doc. position 3 year post. doc. position in Oslo will be announced in a couple of weeks. Will be responsible for SISAK system. Work at OCL and within SISAK SHE collaboration. Can also be involved in investigating thorium (using LLE) for use as fuel in Nuclear Power Plants. Many exciting challenges and possibilities! Slide 51 Slide 52 The end! 9