Chen, X.

Litvinov, Y.

Piotrowski, J.

Sanjari, S.

GSI Repository

Performance of the ESR kicker magnet during E082 ∗J. Piotrowski†1,3, X. Chen1,2, Yu.A. Litvinov1,2, M.S. Sanjari1, and the Two-Body-Weak-Decayscollaboration1GSI, Darmstadt, Germany; 2University of Heidelberg, Germany; 3AGH University of Science and Technology,Krako´w, PolandIn October 2014 the second run of experiment E082“Single-Ion Spectroscopy of Two-Body β-Decays”[1] tookplace. After a shortage of time during the 2012 beamtime,this time 12 days were allocated to performing high preci-sion lifetime measurements of 142Pm. The measurementswere performed by injecting ions and observing them untilthey decayed. The data was analyzed online and offline,and the parameter of interest was the exact timing of eachdecay. In order to get reliable data, one has to assure thatinjected ions are removed from the ESR between injections.In the first experiment we used the injection kick, con-sidering it powerful enough, to also remove the ions fromthe ESR stored from a preceding injection. However it wasnoticed that the kicker magnet, that is used to perform injec-tions, had several documented failures and possibly morethat went unnoticed. This time the experiment was im-proved in two ways: there was a dedicated extraction kickat the end of each cycle, and all kicker magnet pulses weremonitored and saved using a digital oscilloscope.The dedicated extraction kick enabled a visual confirma-tion in the time resolved Schottky spectra that all ions hadbeen extracted. Thanks to the monitoring of kicks, it waspossible to determine exactly what the failure rate of thekicker magnet is during controlled and repeatable opera-tion for over 10000 accelerator cycles, and get quanititativenumbers describing its performance.SetupThe accelerator was operated using a 70 second cycle.Each cycle began with an injection kick which marked thebeginning of data-taking (data acquisition systems weretriggered on injection). Injected ions were observed overa 60 second window. After this time an extraction kick wasperformed, which was followed by a 10 second safety pe-riod to finish data acquisition and saving.The kicker magnet is powered by three power mod-ules. Each module supplies a voltage of up to 80 kV tothe magnet and a single module typically suffices to per-form a successful extraction of the beam. For the exper-iment all three modules were used during both extractionand injection phases. The length of the injection kick wasset to 500 nanoseconds, and the extraction kicks lasted1500 nanoseconds. The assumption was that at a revolu-tion frequency of 2 MHz, an extraction pulse lasting 3 fullrevolutions of the ions would be more than enough to re-move all of them with absolute certainty.∗Work supported by Helmholtz-CAS Joint Research Group HGJRG-108, FP7 Marie Curie ITN “oPAC”, HGF ARD Program† j.piotrowski@gsi.de17.0 17.5 18.0 18.5 19.0 19.5 20.0 20.5 21.0 21.5Amplitude/V10−1100101102103104CountsModule 2 amplitudesextractioninjectionFigure 1: Logarithmic amplitude histogram for module 2.The curves show the extraction (left) and injection (right)amplitudes.ResultsEach power module has a monitoring unit through whicha lower-voltage form of the pulse can be observed. We ac-quired 10359 injection and extraction kicks. We observedthat modules 1 and 3 performed reliably throughout the en-tire experiment. Both delivered a signal with an amplitudeof 20 V for injection and 19 V for extraction kicks, bothof which are the required values for the monitoring signal.The FWHM of the kicks was around 300 mV. We noticed asingle case were the kick was missed by all modules, how-ever as this was a single incident we nonetheless considerthe performance to have been extremely stable.The behaviour of module 2 differed from that of the othermodules. A histogram of the amplitudes for module 2 ispresented in figure 1. For extraction kicks we counted 242cases where kicks were weaker than the average amplitudeby as much as 2 V. The curves for injections and extractionsare visibly different for this one module.SummaryFor the first time in the operation of the ESR, the per-formance of the kicker magnet, crucial to the success ofevery experiment, has thoroughly been investigated. It wasfound that 2 out of 3 modules powering the magnet per-formed without failures in over 10000 accelerator cycles.For module number 2 it was found that the failure rate liesat 0.02%. A value of this magnitude was also confirmed bythe Primary Beams High Voltage Pulsed Power group.Acknowledgments We thank the GSI technical andaccelerator groups for invaluable help during the prepara-tion and conduction of the experiment.References[1] P. Kienle et al., Phys. Lett. B, 726, 638-645 (2013)GSI SCIENTIFIC REPORT 2014 FG-GENERAL-11DOI:10.15120/GR-2015-1-FG-GENERAL-11 429

Performance of the ESR kicker magnet during E082

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Performance of the ESR kicker magnet during E082

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