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Unexplored “north-east” area of the nuclear map

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Unexplored “north-east” area of the nuclear map

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  1. Gas Cell Based Laser Ion Source for Production and Study of Neutron Rich Heavy Nuclei(In Gas Cell Laser Ionization & Separation Setup)Sergey ZemlyanoyFlerov Laboratory of Nuclear Reactions Joint Institute for Nuclear Research Dubna1st Topical Workshop on Laser Based Particle Sources 20-22 February 2013, CERN

  2. Unexplored “north-east” area of the nuclear map fusion 19 known neutron-rich isotopes of cesium (Z = 55) and only 4 of platinum (Z = 78). Above fermium (Z = 100) only proton-rich nuclei are known. fission fragments fragmentation

  3. Abundance of the element in the Universe The 11 Greatest Unanswered Questions of Physics (National Research Council, NAS, USA, 2002): 1. What is dark matter? 2. What is dark energy? 3. How the heavy elements from iron to uranium have been produced? 4. Do neutrinos have mass? … Strong neutron fluxes are expected in core-collapse supernova explosions or in the mergers of neutron stars.

  4. r-process and heavy neutron rich nuclei • difficult to synthesize • difficult to separate

  5. Production on NEW heavy nuclei in the region of N=126(Zagrebaev & Greiner, PRL, 2008) “blank spot” 82 82

  6. Production on new heavy nuclei in the Xe + Pb collisions

  7. Test experiment demonstrates good agreement with our expectations

  8. Simulation of typical experiment in the laboratory frame (1) The yield of new neutron-rich isotopes is maximal at beam energy slightly above the Coulomb barrier (2) Desired reaction products are forward directed (no any grazing features)

  9. Multi-nucleon transfer reactionsas a method for synthesis of heavy neutron rich nucleiandStopping in the gas with subsequent resonance laser ionizationas a method for extracting required reaction products (with a given Z value)

  10. IGISOL – Ion Guide Isotope Separation on line Time profiles of laser-ionized stable Ni-58 from the filament Ni filament He SPIG ~1994 40 kV mass separator + + + Laser beams cyclotron beam target 3-10 mg/cm2 Weak beam, 1nA, 1ms Delay time - down to 10 ms (He) Refractory elements - ! Strong beam, 1uA,20ms Laser-produced Ni ions recombine in a plasma created by a primary beam >99% are neutral We have to provide for radioactive atoms: 1. Efficient laser ionization 2. Survival of laser-produced ions in a volume around the exit hole

  11. Schematic view of setup for resonance laser ionization of nuclear reaction products stopped in gas

  12. Setup consist of the following subsystems

  13. The scheme of the front end of the GALS mass separator subsystem

  14. The layout of the dual chamber laser ion source gas cell • The aim: (by separating stopping and laser ionization chambers) • Increasing laser ionization efficiency at high cyclotron beam current • Increasing selectivity (collection of survival ions) • Working conditions: • cyclotron – DC • Ion collector – DC • Lasers – transverse or longitudinal Exit hole diameter – 0.5mm/1mm Stopping chamber – 4 cm in diameter Laser ionization chamber – 1 cm in diameter

  15. The ion extraction from the gas cell dE ~ 0.7 eV 4.7MHz 0-500V (-210 V) 1200 V 250V The SPIG consists of 6 rods (124 mm long and a diameter of 1.5 mm) cylindrically mounted on a sextupole structure with an inner diameter of 3 mm. The distance between the SPIG rods and the ion source is equal to 2 mm.

  16. Front end of the LISOL mass separator Cyclotron beam Extraction electrode Laser beams Gas Cell SPIG Gas from purifier

  17. Gas cell and Ion-guide system • General requirements to the ion-guide systems look as follows: • pressure in gas cell: 100–500 mbar depending on the energy of reaction products • and required extraction time; • working gas is He or Ar (the latter looks preferably because its stopping capacity • and efficiency of neutralization are higher); • gas purity not lower than 99,9995%; • cell volume is about 100–200 cm3; • vacuum in intermediate camera not worse than 10-2 mbar; • vacuum in the entrance into the mass separator is 10-6 mbar; • Some specific requirements, stipulated by the use of the resonance laser ionization, • should also be taken into account: • gas cell should be two-volume to separate the area of thermalization and neutralization • from the area of resonance laser ionization; • extraction of ions from the cell and driving them into the mass separator have to be provided • by the sextupole radio-frequency system which allows one to increase • the efficiency of the setup and to perform ionization of atoms in the gas jet outside the cell; • the input-output setup must be supplied by the system of optical windows and • by the system of explicit positioning (0.3 mm) of the gas cell, guide mirrors and prisms.

  18. The pump station 3 roots pump station at HV platform Isolating transformer for HV platform • Specifications of the pump station located in the basement: • Pumping system: RUVAC WH 7000 roots pump with SCRELINE SP630 backing pump Leybold Vacuum. • Electrical power for the prepump : 3 X 380V, 11 kW • Electrical power for the pump: 3 X 380V, 18 kW • Weight : 1300 kg, • Noise level : 80 dB(A) - pumps to be placed in the basement with sound isolation panels • Pumping station is placed on the high voltage platform (40kV) and electrical power for roots and • backing pumps comes via the isolation transformer. • - A metal fence with a door and safety switch has to be installed around the pumping station. • - Vacuum gauges and the meter have to be foreseen in the basement.

  19. Gas purifier MonoTorr Phase II 3000 SAES Pure Gas, Inc. Flow meter Brooks Instrument 5860S 0.08 - 8 ln/min Towards gas cell Ar Grade 5.5 (99.9995%) Oil-free, small pump station The scheme of the gas handling and purification system The gas purity is a key issue for efficient running of the laser ion source. The gas handling system has to be designed to supply and to control the gas flow into the gas cell. Electro-polished stainless steel tubes and metal-sealed valves have to be used in order to reduce the outgasing and the "memory effect". The system should be bakeable up to 2000C with temperature control and be pumped by a separate small oil-free pumping station. High-purity argon gas is additionally purified in a getter-based purifier to the sub-ppb level.

  20. Gas purifying system

  21. Mass separator • All extracted ions have charge state +1 because only neutral atoms are ionized to this state • by the lasers while all “non-resonant” ions are removed by electric field before reaching • the area of interaction with laser radiation. In this case the extracted particles can be easily • separated by masses in dipole magnet. • For low-energy (30–60 keV) beams of +1 charged ions no specific requirements are needed • for the dipole magnet. It could be a standard magnet separator similar to ISOLDE II, • for example: • Bending angle 40о–90о, • Bending radius of about 1–1.5 m, • Focal plane length of about 1 m, • Rigidity of about 0.5 Т.m. • Dipole gap about 50-60 mm • Mass resolution is the only critical parameter which should be about 1500. • Camera of the separator must have an optical input if collinear laser ionization • is used with the sextupole ion-guide (SPIG).

  22. Mass separator Most important specifications: Magnet Weight : 1800 kg, Bmax :0.76 T Cooling water flow: 400 l/h, pressure drop = 4 bar Cooling water: 15 degrees Magnet power supply Weight : 250 kg Output : max 300A/25V AC main input: 3 X 380V, 18.5A Cooling water flow: 120 l/h, pressure drop=3bar Vacuum system 4 turbo pumps (at front end, lens chamber, entrance of the magnet, dispersion chamber): for example Edwards STP1003C,Water cooled, 100 l/h per pump Two Prepumps, for example Pfeiffer MVP160-3 can be placed in the basement - Total flow for cooling water: min. 1000 l/h - Compressed air to drive small actuators and vacuum valves - Total electrical power needed : ~20 kW

  23. Comparison dye vs. possible Ti:Sa system Dye Ti:Sa 2x Dye 2x Ti:Sa Ti:Sa 3x Ti:Sa 3x Dye 4x Ti:Sa Dye

  24. l– meter The (almost) optimum RILIS Laser System Nd:YAG Dye 2 SHG Dye 1 THG SHG Master clock NarrowbandDye RILIS Dye Laser System GPS/HRS Delay Generator RILIS Ti:Sa Laser System Target & Ion Source Nd:YAG Ti:Sa 3 Faraday cup Ti:Sa 2 Ti:Sa 1 SHG/THG/FHG l– meter pA – meter

  25. Laser system Credo dye laserspecification (Sirah) • Maximal average power: 20 W at fundamental wavelength, 2 W at 2nd harmonics; • Line width: 1.8 GHz • Pulse duration: ~7 ns • Remote control of wavelength with stabilization to an external laser wavelength meter. Nd:YAG laser specification (EdgeWave GmbH) • Maximal average power: 90 W and 36 W respectively; • Repetition rate: 10-15 kHz; • Pulse duration: 8-10 ns. • Divergence parameter of the green beam: M2 = 1.4; • Electrical power 3.6 kW including 1.6 kW for the water chiller.

  26. The layout of laser installation OT1-OT9 – optical tables; Nd:YAG1 and Nd:YAG2 – pump lasers; DL1-DL3 – dye lasers; R1 and R2 – racks for electronics and water chillers; M1-M10, M22 – high power mirrors for 532nm beams; M10-M15 – high power mirrors for 355nm beams; BS1-BS4 – beam splitters for 532nm beams; M16-M21, M23-M25 – mirrors for dye laser beams; T1-T4 – telescopic zoom expanders for 532nm beams; T5 and T6 - telescopic zoom expanders for 355nm beams; L1-L6 – spherical lenses, SM1 and SM2 – spherical mirrors; BD1 and BD2 – beam dumps for IR beams; P1 and P2 – half-wave plates for 355nm; RM1-RM4 – return mirrors for reference beams; RP – reference plane; AlM1 – Al mirror; QP1 – quartz plate; RC – reference cell

  27. The laser system view

  28. Rooms requirements for this setup

  29. Possible position of SETUP at cyclotron U400M

  30. Working plan

  31. Conclusion • At target thickness 0.3 mg/cm2, ion beam of 0.1 pmA and setup efficiency of 10% we would be able to detect 1 event per second at cross section of 1 microbarn • It allow as to measure decay properties at least 1 new isotope per day • It is sufficiently not only for measurement of typical nuclear characteristics (like half-life times, decay schemes, etc.), but also for determining of nuclear charge radii (and moments) with using in-source laser spectroscopy.

  32. People involved into developing and discussion of this SETUP project Leuven:M. Huyse, Yu. Kudryavtsev, P. Van Duppen Jyväskylä:Juha Äystö, Iain Moore, Heikki Penttilä CERN:Valentin Fedosseev GSI:Michael Block, Thomas Kühl GANIL:Nathalie Lecesne, Herve Savajols Mainz:Klaus Wendt Manchester:Jonathan Billowes, Paul Campbell iThemba LABS: Robert Bark + 2 PhD students Egypt: Hosam Othman IS RAN Troitsk:Vyacheslav Mishin FLNR JINR:V. Zagrebaev, S. Zemlyanoi, E. Kozulin, and others

  33. People involved into developing and discussion of this SETUP project Thank you for your attention

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