1 / 51

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) ,

teal
Télécharger la présentation

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

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. 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

More Related