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DORIS - 2 GeV Experiences in 2011

DORIS - 2 GeV Experiences in 2011 . Olympus Collaboration Meeting April 27th, 2011 F.Brinker. Startup after the shutdown , Feb. 10 th. Starting with positrons at 4.5 GeV Main magnets set to theory values Correctors set to 2010 values and zero in RF- straight

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DORIS - 2 GeV Experiences in 2011

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  1. DORIS - 2 GeV Experiences in 2011 Olympus Collaboration Meeting April 27th, 2011 F.Brinker

  2. Startup after theshutdown, Feb. 10th • Startingwithpositronsat 4.5 GeV • Main magnetssettotheoryvalues • Correctorssetto 2010 valuesandzero in RF-straight • Empiricallyfindingtrajectory • Passingtargetcellwithoutproblems • Oneweekofbakeoutrunswithcurrentofupto 130 mA in 10 bunches

  3. Feb. 17 th: First e+ 2.0 GeV run • Setting up DORIS and transport line with theoretical optic and correctors from 4.5 GeV downscaled. • Adjusting DESY extraction energy to match transport line • Optimize DORIS injection • First time target gas filled with beam

  4. Feb. 18 th: Second e+ 2.0 GeV run • First stored beam within 1 hour after 4.5 GeV run • Optimize feedback settings, tunes, orbit • Switch back to 4.5GeV within 20 min. Feb. 21 st: Third e+ 2.0 GeV run • Switching between 4.5 and 2.0 GeV within 20 min.

  5. Feb. 22 nd: First e- 2.0 GeV run • Just using positron files with reversed polarity • Stored beam after 2 hours • Switch back to 4.5GeV e+ within 25 min.

  6. Feb. 23 nd: 4th e+ 2.0 GeV run, RF-optimization • Maximum current which can be filled depends strongly on RF-settings • RF-system isoptimized for 4.5 GeV runswith 8 cavities, 7.2 MV andabout 800 kW of RF-power • At the very low power needed for 2 GeV the RF-signals and Feedbacks are not reliable • Thereforewetriedto „detune“ thecavities – shifttheresonancefrequencyawayfromthetransmitterfrequency. This reducesthequalityfactorandincreasestheneeded RF-power

  7. Lifetimedefinedbythetargetdensity down to 0.5 hoursattwicethe nominal density • After thatrunit was decidedtoremovethetargetchamber due tothe extreme temperatureincreases

  8. Run duringserviceweek on April 14 th • Switching to 2.0 GeV within 20mins. Using the files from February • 8 Cavities detuned by defined phase ( 4 Cavities at the limit of tuning!) • Long. FB working with 2 amplifiers now → Lower cavity voltage also means longer bunches and less transient heating …

  9. Summary • The new Olympus opticcouldeasilybeestablishedandworkeswell also for thesynchrotron light users • Longitudinal instablitieslimitthe max. stable beam currentat 2.0 GeV ( nootherlimitsobserved so far ) • Obviouslythe RF detectorsand RF-feedback loopsare off theirlimits • Detuningofthecavitiesandthusincreasingthe RF-power significantlyincreasesthecurrentlimit • Over 7 hoursnoneofthefamous „dustevents“ couldbeobservedwithelectrons

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