Dissertation Submitted to the Combined Faculties for the Natural
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Dissertation submitted to the Combined Faculties for the Natural Sciences and for Mathematics of the Rupertus-Carola University of Heidelberg, Germany for the degree of Doctor of Natural Sciences presented by Dipl.-Phys. Stephen Koszudowski born in Bad Soden/Ts., Germany Oral examination: 08.07.2009 Developments for the HITRAP Cooler Trap and mass measurements around A=96atSHIPTRAP Referees: Priv. Doz. Dr. Wolfgang Quint Prof. Dr. Andreas Wolf Developments for the HITRAP Cooler Trap and mass measure- ments around A = 96 at SHIPTRAP Die HITRAP-Anlage (Highly charged Ions Trap - Falle f¨ur hochgeladene Ionen) wird zur Zeit an der GSI in Darmstadt aufgebaut und in Betrieb genommen. Sie wird B¨undel von 105 hochgeladenen schweren Ionen, z.B. wasserstoffartigem Uran (U91+), f¨ur hochpr¨azise atomphysikalische Experimente zur Verf¨ugung stellen. Die Ionen werden vom GSI-Beschleunigerkomplex produziert und im Experi- mentierspeicherring auf 4 MeV/u abgebremst. Ein zweistufiger Linearab- bremser entschleunigt die Ionen dann auf 6 keV/u. Die erste Abbremsstufe auf 500 keV/u wurde erfolgreich in Betrieb genommen. Die abgebremsten Ionen werden in eine Penning-Falle injiziert (die K¨uhlerfalle), wo sie mit Hilfe von Elektronen- und Widerstandsk¨uhlen auf 4 K abgek¨uhlt werden. Resonante Schwingkreise zum zerst¨orungsfreien Nachweis und zum Wider- standsk¨uhlen der gefangenen Teilchen wurden konzipiert und getestet. Die Zeitsteuerung des Fallenzyklus (Ionen-Einfang, K¨uhlen, Extraktion) mit einer Aufl¨osung von 25 ns wurde in das Kontrollsystem CS integriert. CS wird auch an der Massenmessungs-Penning-Falle SHIPTRAP verwendet, wo die neue Zeitsteuerung erfolgreich genutzt wird. SHIPTRAP vermisst radioak- tive Ionen, die in Fusions-Evaporations-Reaktionen am Geschwindigkeitsfil- ter SHIP produziert werden. Die Massen von 9 Nukliden (93,94,95Technetium, 94,96Ruthenium, 95,96,97,98Rhodium) nahe der Stabilit¨at wurden pr¨azise ver- messen und mit der Atomaren Massen Evaluation verglichen. Der Nachweis vonisomerenZust¨anden mit SHIPTRAP wurde untersucht. Developments for the HITRAP Cooler Trap and mass measure- ments around A = 96 at SHIPTRAP The HITRAP (Highly charged Ions Trap) facility is currently being set up and commissioned at GSI in Darm- stadt. It will provide bunches of 105 heavy highly-charged ions, for example hydrogen-like uranium (U91+), to high-precision atomic physics experiments. The ions are produced by the GSI accelerator complex and decelerated to 4 MeV/u in the Experimental Storage Ring. Then the ions are decelerated by a two-step linear decelerator down to 6 keV/u. The first deceleration step down to 500 keV/u was successfully commissioned. The decelerated ions are injected into a Penning trap (the Cooler Trap), where they are cooled to 4 K by electron and resistive cooling. Resonant circuits for non-destructive detection and the resistive cooling of the trapped particles were designed and tested. The time control of the trap-cycle (trapping, cooling, extraction) with a time resolution of 25 ns was implemented into the control system CS. CS is also used at the mass measurement Penning trap SHIPTRAP, where the new time control is successfully operated. SHIPTRAP measures radioactive ions stemming from fusion evaporation reactions at the velocity filter SHIP. The masses of 9 nuclides (93,94,95Technetium, 94,96Ruthenium, 95,96,97,98Rhodium) near the line of stability were precisely measured and compared with the Atomic Mass Evaluation. The detection of isomeric states with the present SHIPTRAP set-up was studied. for N2 +x It is a mistake to think you can solve any major problems just with potatoes. Douglas Adams Contents 1 Introduction 1 2 HITRAP and SHIPTRAP within GSI 7 2.1Penningtrapbasics......................... 7 2.2IonproductionatGSI....................... 10 2.2.1 Productionofhighlychargedions............. 10 2.2.2 The accelerator complex at GSI .............. 12 2.3 The SHIPTRAP facility ...................... 12 2.3.1 ThevelocityfilterSHIP.................. 12 2.3.2 TheSHIPTRAPgascell.................. 15 2.3.3 The RFQ buncher and transfer section .......... 17 2.3.4 TheSHIPTRAPPenningtraps.............. 18 2.4 The HITRAP facility ........................ 21 2.4.1 Overview.......................... 21 2.4.2 TheDouble-Drift-BuncherandtheIH-Linac....... 23 2.4.3 The Radio Frequency Quadrupole Decelerator . .... 27 2.4.4 TheLowEnergyBeamTransport(LEBT)........ 28 2.4.5 TheCoolerTrap...................... 31 2.4.6 TheVerticalBeamlineandEBIT............. 32 2.4.7 HITRAPexperiments................... 34 3 The HITRAP Cooler Trap 37 3.1ThedesignoftheHITRAPCoolerTrap............. 37 3.1.1 WorkingcycleoftheCoolerTrap............. 39 3.2IondetectionandmanipulationatHITRAP........... 41 3.2.1 FT-ICR........................... 41 3.2.2 Coolingoftheionmotion................. 43 3.3Cryogenicelectronics........................ 45 3.3.1 Theelectronicsbox..................... 46 3.3.2 Thecoils........................... 47 3.3.3 Cryogenicpreamplifier................... 58 3.3.4 Filters............................ 60 3.4Roomtemperatureelectronics................... 64 3.4.1 Powersupplies....................... 64 3.4.2 Detectionelectronics.................... 64 I II CONTENTS 4 Cooler trap control system 67 4.1Trapcycle.............................. 67 4.2Controlsystem........................... 69 4.2.1 Requirementsonthecontrolsystem............ 69 4.2.2 CS .............................. 69 4.2.3 Implementation of the CS-system............. 70 4.3Theinterfacetothetimingsystem................ 71 4.4Thetimingsystem......................... 71 4.4.1 Requirementsonthetimingsystem............ 71 4.4.2 The NI PCI-7811R FPGA card .............. 72 4.4.3 Designofthetimingsystem................ 73 4.4.4 Implementationandperformance............. 75 5 On-line mass measurements at SHIPTRAP around A =96 79 5.1Experimentalresults........................ 82 5.2Dataanalysisprocedure...................... 85 5.3DataEvaluationandAtomicMassEvaluation.......... 87 5.3.1 Statistical analysis on the resolving power of the two- resonancesfit........................ 90 5.3.2 Discussionoftheisomericstateadmixtures........103 5.4Discussionoftheobtainedresults.................105 5.4.1 Comparison between this work and the Atomic Mass Evaluation..........................105 5.4.2 Discussionoftheresults..................107 6 Summary, conclusions and outlook 109 A Fast-Fourier-Transformation 113 B Detailed description of the timing software 115 Bibliography 121 Acknowledgments 135 List of Tables 2.1 Calculated performance of the decelerator elements. ...... 23 3.1Q-factorsfromthemeasurementofthe440kHzcoil......... 53 3.2Q-factorsfromthemeasurementofthe35MHzcoil......... 57 3.3 Amplification of the cryogenic amplifier with respect to the bias voltages 61 5.1Half-life,spinandparityofthemeasurednuclides.......... 82 5.2Experimentalresults........................... 84 5.3Atomicmassresults........................... 89 5.4 Results of the statistical analysis on the isomer resolution for the spectrawithoutjitter........................... 96 5.5 Results of the two resonances fit with distance and weight running . 96 5.6 Results for the statistical analysis on the isomer resolution for spectra withjitter................................. 99 5.7 Results of the t-test on the mean χ2 ofthesingleandthetworeso- nancesfit................................. 100 III IV LIST OF TABLES List of Figures 1.1RegionsofthenuclearchartaddressedbySHIPTRAP........ 2 1.2 Electrical field strength in low-lying states of hydrogen-like ions. 4 2.1Penningtrapschematics......................... 8 2.2IonmotionsinaPenningtrap...................... 9 2.3CompensatedcylindricalPenningtrap................. 10 2.4 Overview of the GSI accelerator complex. ............. 11 2.5 Overview on the SHIPTRAP facility. ............. 13 2.6OverviewoftheSHIPvelocityfilter................... 14 2.7TheSHIPTRAPgascell......................... 15 2.8 Schematic of the SHIPTRAP RFQ buncher. ............. 17 2.9SchematicoftheSHIPTRAPtransfersection.............. 18 2.10SchematicoftheSHIPTRAPPenningtraps.............. 19 2.11Time-of-flightresonance.......................... 20 2.12HITRAPoverview............................ 22 2.13TheDoubleDriftBuncher........................ 24 2.14TheIH-linac............................... 25 2.15 Decelerated beam after the IH-linac . ............. 26 2.16Theradio-frequencyquadrupole..................... 27 2.17Velocityindependentionlossduetochargeexchange......... 28 2.18 Electrostatic potential and magnetic flux on the LEBT axis . 29 2.19TheLEBTinstalledinthereinjectionchannel............. 30 2.20LEBTEinzel-lens............................. 30 2.21NestedtrapconfigurationoftheCoolerTrap............. 31 2.22TheVerticalBeamTransport...................... 33 3.1WorkingcycleoftheCoolerTrap.................... 40 3.2 Electron cooling of 105 U92+ ions.................... 44 3.3Theelectronicsbox............................ 47 3.4Theaxialfrequencycoil......................... 48 3.5Thecyclotronfrequencycoil....................... 50 3.6Q-measurementset-up.......................... 51 3.7 Example for a resonance for the transmission-type Q-measurement . 52 3.8Mechanicalset-upofthe440kHzcoil................. 53 3.9Cross-andbasket-windingtechniqueforcoils............. 54 3.10Reflection-typemeasurementintheSmith-chart........... 56 3.11Thecryogenicpreamplifier........................ 59 3.12Amplificationversusgate1voltage................... 60 3.13Amplificationversusfrequency..................... 61 V VI LIST