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WITCH - a first determination of the beta-neutrino angular correlation

WITCH - a first determination of the beta-neutrino angular correlation. S. Van Gorp, M. Breitenfeldt , V. De Leebeeck,T. Porobic, G. Soti, M. Tandecki, N. Severijns (K.U.Leuven, Belgium) , P. Friedag, C. Weinheimer (Univ. Munster, Germany) , M. Beck (Univ. Mainz, Germany) ,

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WITCH - a first determination of the beta-neutrino angular correlation

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  1. WITCH - a first determination of the beta-neutrino angular correlation S. Van Gorp, M. Breitenfeldt , V. De Leebeeck,T. Porobic, G. Soti, M. Tandecki, N. Severijns(K.U.Leuven, Belgium), P. Friedag, C. Weinheimer(Univ. Munster, Germany), M. Beck (Univ. Mainz, Germany), V. Kozlov, F. Gluck(Univ. Karlsruhe, Germany), D. Zakoucky(NPI-Rez, Prague, Czech), E. Liénard, X. Fléchard, C. Couratin, G. Ban (LPCC, Caen, France)

  2. Overview • Motivation • Experimental Setup • WITCH status • Measurement of a on 35Ar • Penning trap and MC Simulations • Extracting a 2/19 Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  3. Motivation EXP: |CS/CV| < 0.07 |CT/CA| < 0.09 WITCH measures the beta-neutrino angular correlation coefficient, a. Which is extracted from the recoil energy of the nucleus after beta-decay. =>Search for scalar (or Tensor) Interactions Low energy (couple 100 eV)! • Need for scattering free source 3/19 Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  4. ~7m Experimental Setup 4/19 Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  5. Retardation spectrometer traps Ion reflected if Energy_ion < Energy_retardation retardation barrier is changed and #ions coming over the barrier are counted. Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011 Energy conversion

  6. Isotope selection • Interesting from a physics point of view • Production yield @ ISOLDE ~ 106/107particles per second • Half-life: order of 1 s • Stable daughter isotope • Decay mode: b-(± 10 times more recoil ions than b+) • Due to shake-off the daughter ion can have a charge-state up to 5+ • Minimal isobaric/isomeric contamination • Simple decay scheme • => 35Ar Simon Van Gorp – TCP Saariselkä- 14.04.2010

  7. WITCH overview before run 2011 • November 2009: • Measurement on 35Ar showed voltage dependent ionization • June 2010: • Measurement with 144Eu, unfortunately a mixed cocktail beam from ISOLDE. Too low statistics to extract a recoil spectrum. • Wire to reduce the secondary ionization proved to work. • November 2010: • Magnetic Shielding and RFQoperational. WITCH can work in parallel with REX-ISOLDE! -> Much more testing time: necessary for a precision experiment! • would be even better at ISOL@MYRRHA • June 2011 • Measuring a recoil spectrum on 35Ar 7/19 Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  8. 35Ar: unwanted ionization • Nov 2009 run on 35Ar • 6 seconds spectrum • Retardation voltage (0 -> 500V) • from 1.5-3.5s • Ionization depends on the retardation barrier voltage. 8/19 Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  9. - e + ionization + + e e e + e e e secondary electron emission e + Unwanted Penning Trap in WITCH • Retardation barrier for ions • = • Potential well for e- • trapped e- in the spectrometer ionize rest gas which is creating ionization. • Installation of a wire in the spectrometer. • If an e- hits this wire it will be picked up by the power supply and lost. • -> Effective method to empty the unwanted Penning trap. Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  10. Solution: the spectrometer wire • Measurement on 144Eu (June 2010) with the wire installed. No ionization observed. • => Ready for a measurement on 35Ar in 2011 10/19 Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  11. Experimental conditions • ISOLDE target broke few days before the actual run. Replaced with used target. => low 35Ar yield (5.105 compared to 2.107 in yieldbook) • HV electrode could not be operated as intended. Not-optimal focus of the electrodes caused a loss off 40% • Losses in the decay-trap • -> A low statistics experiment. • losses in the decay-trap due to • non-optimized voltages and • timings. • The red curve (better settings) • shows a more constant • behavior Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  12. measurements • Normalization on • # ions in decay-trap • = #ions in overshoot • peak • 500 ms cooling in the cooler-trap. Afterwards capture in the decay-trap. • Measurement with and without retardation voltages. Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  13. normalization • Difference of measurements with and without retardation voltage applied. (normalized with #ions decay-trap). • Correct the data for 35Ar half-life and losses in the decay-trap. Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  14. Simulations: • Compare obtained spectra with simulated spectra. Therefore: • 1. Simbucasimulates the ion-cloud in the decay-trap. • 2. Ion-cloud parameters are fed to a MC simulation program (SimWITCH). • Comsolmultiphysics program is used to extract electric fieldmaps given the electrode voltages • Magnetic fieldmaps from the magnet manufacturer • Buffergas collisions and excitations are handled by Simbuca Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  15. Simulations: SimWITCH • Ions are not properly focused on the MCP, due to the lower HV settings • applied. The applied voltages are not high enough to ‘pull’ the ions of the • magnetic field lines. Input spectra 2+ 1+ • - Ions are lost on SPDRIF01 electrode. • - The higher the charge-state of the daughter ion the better the focus. Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  16. Simulations to extract a • Simulations for • All retardation voltages (0V, 150V, 250V, 350V, 600V) • All charge states (1+,2+,3+,4+,5+) • 1+ : 77% • 2+: 16% • 3+: 5% • 4+,5+: 2% • Including the charge state distribution (as measured with LPC trap) we can extract %ions reaching the MCP depending on the retardation step and a • -> Fit the data with a linear combination of a=1 and a=-1 to obtain the final result for the beta-neutrino angular correlation factor a. Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  17. Extracting a • 7000 ions in spectrum. a=-1 a=1 a=0.80 (49) • The preliminary result from the analysis yields a = 0.80 (49)statc2/N= 0.72 • SM value of a =0.9004(16). • Not including actual experimental conditions yields a = 5.98 (97) !! => • This stresses the importance of simulations!! Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  18. Conclusion and outlook • Conclusion: • - Seem to have solved unwanted ionization • - Magnetic shield and RFQ allow much more testing time. • - First determination of a on 35Ar with the WITCH experiment. • Outlook: • - Upcoming experiment end October. • Count rate can be improved by: 10 (ISOLDE) * 50 (measurement time) * 2 (measurement cycle) * 2 (focussingelectrode efficiency) * 4 (tuning in the B-field) = 8000 times more statistics • -> sqrt(8000)=90 meaning that it is possible to reduce the statistical error to 0.5 % Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  19. Acknowledgements Thank you for your attention.

  20. Backup slides Simon Van Gorp – TCP Saariselkä- 14.04.2010

  21. + e + ionization e e + e e + e e secondary electron emission e + Unwanted discharges: Townsend discharge - - Townsend discharge (bad vacuum, with or without magnetic field) g-> create e- ionization collisions with gas molecules  secondary electrons and positive ions; secondary emission on cathode due to positive ion impact  more electrons  more ionization collisions  more secondary electrons and ions avalanche, self sustained discharge 21/21 Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  22. - e + ionization + + e e e + e e e secondary electron emission e + Unwanted Penning Traps Penning Discharge (good vacuum, with magnetic field) - trapped e-spend long time between cathode and anode large pathlength  increased probability for discharge, even in good vacuum 22/21 Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  23. Additional proof for recoil ions • Pulse height distribution of the ions is also registered. • This is typically exponential for beta-particles and dark counts. And bell • shaped for ions. Simon Van Gorp – TCP Saariselkä- 14.04.2010

  24. Simulations: Simbuca • Due to limited time the traps were not properly optimized: • Transfer time was not set ideally 32.5 us instead of 38.5 us. • -mean energy of 4.5 eV (instead of 0.2 eV) • -ions positions in the decay-trap is 15 mm lower than the center. Simon Van Gorp - low-energy fundamental-interactions physics at ISOL@MYRRHA – 4 okt 2011

  25. Stable testing environment • WITCH magnet interferes with Rex-runs • Magnetic mu-metal shielding around part of the Rex-EBIS • Possibility to run WITCH in parallel with a 3T magnetic field. • WITCH ion source has low intensity and is continuous <-> high intensity pulsed ISOLDE beam • Small RFQ (15 cm) in combination with the ion source. • RFQ can deliver bunches of 10^7 ions with 2.5 us time spread. Picture shielding Simon Van Gorp – TCP Saariselkä- 14.04.2010

  26. Simulation Motivation • Data analysis by particle tracking routine to recreate a spectrum. A good understanding of the source of ions is needed. • Parameters to characterize • Temperature (=Energy) • # ions • Position distribution • WITCH: 106-7 ions per cycle • -> Computer simulations are dominated by the Coulomb interaction calculation • Solution: use a Graphics card to simulate • Coulomb interactions. Development of the Simbuca simulation package 26/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  27. Chamomile scheme: practical usage • Function provided by Hamada and Iitaka [2]: • Gravitational force ≈ Coulomb Force • Conversion coefficient: • Needed: - 64 bit linux • - NVIDIA Graphics Card that supports CUDA • - CUDA environment v3.x • Not needed: - CUDA knowledge • - … [2]: http://arxiv.org/abs/astro-ph/0703100 , 2007 27/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  28. The spectrometer wire • Good correspondence between simulation and experimental data. • The creation of the ionization can be stopped with installing a wire. • We understand the ionization effect and • More tests with a centered wire will be done • Measurement on 144Eu (June 2010) with the wire installed • -> no ionization was seen 28/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  29. GPU vs CPU • GPU blows the CPU away. The effect becomes more visible with even more • particles simulated. • Simulating 4000 ions with a quadrupole excitation for 100ms with buffer gas. Takes 3 days • with a GPU compared to 3-4 years with a CPU! GPU improvement factor CPU and GPU simulation time 29/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  30. Simbuca overview • Simbuca is a modular Penning Trap simulation package that can be applied to simulate: • Charged particles (+/- /N charges) • Under the influence of B and E fields • With realistic buffer gas collisions • Coulomb interaction included • Can run on GPU and CPU • http://sourceforge.net/projects/simbuca/ • http://dx.doi.org/10.1016/j.nima.2010.11.032 Simulation of Ion Motion in a Penning trap with realistic BUffer gas collisions and Coulomb interaction using A Graphics Card. 30/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  31. Usage of the program • WITCH • Behavior of large ion clouds • Mass separation of ions • Smiletrap (Stockholm) • Highly charged ions • Cooling processes • ISOLTRAP (CERN) • In-trap decay • Determine and understand the mass selectivity in a Penning trap • ISOLTRAP(Greifswald) • isobaric buncher, mass separation and negative mass effect • CLIC (CERN) • Simulate bunches of the beam 31/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  32. Quadrupole excitation • Mass selective excitation on the • frequency wc = q.B/m • Continuous conversion between • Magnetron and cyclotron radii. • The cyclotron radius is cooled by • Buffer gas collisions • -> mass selective centering/cooling of ions • The size of the final ion cloud one can • reach is influenced by the Coulomb • interaction 32/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  33. Quadrupole excitation – movie • Argon (150 ions ) and Chlorine (ions) mixture • 10ms wc excitation quadrupole excitation • 5ms w- dipole excitation • wc excitation quadrupole excitation 33/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  34. frequency scans • The effect of the Coulomb interaction is not yet understood • All highly depended on mass, amplitudes, times of excitations… # particles / 100 34/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  35. Conclusion • The WITCH experiment • New traps installed • We understand the small ionization trap in the spectrometer • More tests with a (centered) wire will be done before the next beam time • The Magnetic shielding works -> WITCH can work in parallel with REX-ISOLDE • The Simbuca Code • A big simulation-timegain to calculate Coulomb interactions on a GPU • A new tool to investigate how large ion clouds are behaving and to explain observed frequency shifts • Necessary for WITCH and being used by other groups • Will be compared to experimental data in upcoming months 35/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  36. Retardation spectrometer A potential barrier is applied and the #ions going over the barrier are counted with an MCP detector. This potential barrier is changed -> A spectrum is measured. 36/21 Simon Van Gorp - Scientific meeting - 16.02.2011

  37. WITCH History • 2006 first recoil spectrum measured 124In • First notice of discharges • Electrodes could not be operated as intended • 2007 physics run 35Ar • Discharges returned • Stable 35Cl+ domination in the beam • Trap-halflife of 35Ar+ was 8 ms • Electrodes could not be operated as planned • 2008 • Technical improvements • Vacuum upgrade • All-metal buffer gas 500V spectrometer potential (V) 0V Simon Van Gorp - Scientific meeting - 10.06.2009

  38. Discharges: example • Huge increase in count rate • Can happen in couple of hours/minutes • Unexpected • Some discharges only happen in combination with a g source The energy barrier was set to +500 V in the first 3.4 seconds. After this the spectrometer switches to 0 V and it awaits the next cycle. 3 types of discharges Townsend discharge (bad vacuum) Vacuum breakdown (sharp electrodes) Penning Discharge (combination of B and E field) Simon Van Gorp - Scientific meeting - 10.06.2009

  39. Coulomb interactions • Coulomb force scales with O(N2) • Tree methods (Barnes Hut, PM, P3M, PIC, FMM) • reduces this to O(N log N) • Space is divided in nodes. Which are subdivided • A node has the total charge and mass, and is • located on the centre of mass. • Approx. long range force by aggregating particles • into one particle and use the force of this one • particle • Scaled Coulomb Force puts more weight to the charge of one ion to simulate more ions. Works well [1] [1]: D. Beck et al, Hyp. Int. 132, 2001 Simon Van Gorp – TCP Saariselkä- 14.04.2010

  40. Why a GPU? • GPU • -high parallelism • -very fast floating point calculations • -SIMD structure (pipelining!) • Stream processor • ≈ CPU • = Comparable with a factory assembly line with threads being the workers • Geforce 8800 GTX Simon Van Gorp – TCP Saariselkä- 14.04.2010

  41. Secondary ionization (2009) • July 2009; measurement with same 60Co as before (70% of the source strength, t1/2 ~ 1925d) •  Clear effect on background 20% higher when spec@ 450 V •  only 2.5 cps Much more decays are expected for 35Ar spectrometer potential (V) 450V 0V Michaël Tandecki - Werkbespreking – 09/12/2009

  42. Charge exchange (with Ar) • Situation in 2007: • ‘Charge exchange half-life’ in REXTRAP; 75 ms • in WITCH; 8 ms (= not enough to cool) Michaël Tandecki - Werkbespreking – 09/12/2009

  43. Charge exchange: improvements He-57 gas bottle All-metal reducer Needle valve To turbo pump NEG pump All-metal angle valves Full-range gauge Michaël Tandecki - Werkbespreking – 09/12/2009

  44. Most important issues with 35Ar in 2007 • Isobaric contamination from 35ClDuring the run: 25 times more Cl than Ar • Charge exchange with buffer gasWe couldn’t cool the ion cloud, because the ions were neutralized before being cooled • Secondary ionization‘Noise’/discharges showing up when switching the spectrometer Michaël Tandecki - Werkbespreking – 09/12/2009

  45. Electropolishing the electrodes before after 2 cm Most probably the reason why the huge discharge in the spectrometer is gone. Discharge with g-source gone! Simon Van Gorp - Scientific meeting - 10.06.2009

  46. Chamomile scheme • Calculating gravitational interactions on a Graphics Card via the Chamomile scheme from Hamada and Iitaka (in 2007). • Why a GPU? • -parallelism! • -only 20 float operations • -CUDA programming • language for GPU’s • i-particles piece available for each ‘assembly line’ • j-particles piece presents itself sequentially to each line • force is the output of each line [2]: T. Hamada and T. Iitaka, arXiv.org:astro-ph/0703100, 2007 Simon Van Gorp – TCP Saariselkä- 14.04.2010

  47. Improving the vacuum • Vacuum systemdry scroll pumps instead of rotary pumps extra valves in front of turbos for ‘vacuum safety’ • Detector electropolishing of surrounding electrode • Spectrometer redesign of some electrodes electropolishing of re-acceleration electrodes NEG foil around biggest retardation electrode • Traps better Ti (>< Al) structure buffer gas system is ‘all-metal’ now NEG foil + resistive heater around the traps • VBLteflon electrode connections gone installation of NEG coated chambers non-UHV compatible materials gone (Zn, …) • HBLuntouched Simon Van Gorp - Scientific meeting - 10.06.2009

  48. High voltage / re-acceleration Michaël Tandecki - Werkbespreking – 09/12/2009

  49. High voltage / re-acceleration Michaël Tandecki - Werkbespreking – 09/12/2009

  50. High voltage / re-acceleration SPACCE01SPACCE02SPEINZ01SPDRIF01SPDRIF02Detector MCP Compensation magnet Optimal settings normal settings Recently obtainedSPACCE01 -2 kV -1.4 kV -2 kV SPACCE02 -10 kV -2 kV -8 kV SPEINZ01 -200 V -500 V -500VSPDRIF01 -10 kV -550 V -8 kV SPDRIF02 -10 kV -7 kV -9 kV Michaël Tandecki - Werkbespreking – 09/12/2009

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