Dark current measurement at PITZ setup Gun dark
- Slides: 8
Dark current measurement at PITZ setup Gun dark current measurements Booster dark current measurements Summary Igor Isaev Unwanted Beam Workshop 2012 Humboldt-University Berlin, 17 -18. 12. 2012
PITZ Setup High energy part ( up to ~25 Me. V/c) Low energy part ( up to ~6. 7 Me. V/c) DCM 1 Dipole CDS Booster FC 1 Dipole RF Photo Gun ICT 14 -cell, L-band, normal-conducting copper Cut Disc Structure (CDS) Max. RF power 8. 6 MW Max. gradient 14 MV/m. Max. momentum gain 25 Me. V/c. Max. pulse length 900 ms. Repetition rate 10 Hz Igor Isaev | Operating temperature 44 o. C. 1. 6 -cell L-band, normal conducting copper photocathode RF cavity Max. RF power 7 MW Max. gradient 60 MV/m Max. momentum gain 6. 7 Me. V/c Max. pulse length 700 ms Repetition rate 10 Hz Unwanted workshop 2012 | 17 -18. 12. 2012 | Seite 2 Cathode beam material Cs 2 Te. Operating temperature 78 o. C
Gun 4. 1 dark current measurements at PITZ 01. 06. 2012 Dark current as a function of main solenoid current 5. 6 MW power in the gun 250 us RF pulse duration 4. 1 MW power in the gun 750 us RF pulse duration. Igor Isaev | Unwanted beam workshop 2012 | 17 -18. 12. 2012 | Seite 3
Gun dark current measurements Dry-ice sublimation-impulse cleaning significant dark current reduction Dark current in Faraday cup versus RF power for different Guns and cathodes Gun 3. 1 (HPWR), 2006 -05 -08, Cs 2 Te#58. 1 Gun 3. 2 (HPWR), 2007 -08 -05, Cs 2 Te#42. 4 Gun 4. 2 (CO 2), 2008 -08 -31, Mo#113. 1, 400µs 5000 Gun 4. 2 (CO 2), 2008 -09 -01, Mo#113. 1, 700µs Gun 4. 2 (CO 2), 2008 -09 -15, Cs 2 Te#23. 3, 200µs Vertical cleaning setup with 110 o rotating nozzle. Maximum dark current [µA] Gun 4. 1(CO 2) 2011 -06 -06 N, Cs 2 Te #625. 1, 150 us 4000 Gun 4. 1(CO 2) 2012 -01 -03 A, Mo #133. 1, 200 us Gun 4. 1(CO 2) 2012 -06 -01 A, Cs 2 Te #11. 3, 250 us Gun 4. 1(CO 2) 2012 -06 -01 A, Cs 2 Te #11. 3, 750 us 3000 2000 1000 0 0 1 2 3 4 5 RF power in the gun [MW] 6 Igor Isaev | Unwanted beam workshop 2012 | 17 -18. 12. 2012 | Seite 4 7 8
Detailed gun dark current measurements 600 Gun 4. 2 (CO 2), 2008 -08 -31, Mo#113. 1, 400µs Gun 4. 2 (CO 2), 2008 -09 -01, Mo#113. 1, 700µs Gun 4. 2 (CO 2), 2008 -09 -15, Cs 2 Te#23. 3, 200µs Maximum dark current [µA] 500 Gun 4. 1(CO 2) 2011 -06 -06 N, Cs 2 Te #625. 1, 150 us Gun 4. 1(CO 2) 2012 -01 -03 A, Mo #133. 1, 200 us Gun 4. 1(CO 2) 2012 -06 -01 A, Cs 2 Te #11. 3, 250 us 400 Gun 4. 1(CO 2) 2012 -06 -01 A, Cs 2 Te #11. 3, 750 us 300 200 100 0 3, 7 4, 2 4, 7 5, 2 5, 7 6, 2 6, 7 7, 2 RF power in the gun [MW] Igor Isaev | Unwanted beam workshop 2012 | 17 -18. 12. 2012 | Seite 5
Gun 4. 1 multipacting measurements FC signal RF reflected power signals Dark current Multipacting Solenoid scan maps for multipacting measurements Igor Isaev | Unwanted beam workshop 2012 | 17 -18. 12. 2012 | Seite 6
Booster dark current measurements Booster geometry Current measurements • • Measurement was done using Dark Current Monitor (DCM) Measured DC @ FC 1 is ~10 times lower DC spectrum measurements Measurement was done downstream in High Energy dispersive arm • • • Well pronounced bumps Three cells have the most contribution Three bumps are missing in low energy part of the spectrum Igor Isaev | Unwanted beam workshop 2012 | 17 -18. 12. 2012 | Seite 7
Summary > Significant dark current reductions can be obtained by the dry-ice sublimation-impulse cleaning procedure. > The latest measured dark current from the gun is about 400 µA for the ~5. 5 MW power with 250 µs pulse duration and 70 µA for the 4 MW power with 750 µs pulse duration > Solenoid scan maps are performed for multipacting measurements > Booster dark current of up to 1. 8 m. A was measured with the DCM upstream the cavity at full power of 6. 6 MW > The spectra measurement showed periodic structure similar to the simulations, with more distinct bumps and different relative intensity > Three lowest energy bumps are missing, next three deliver the highest dark current Igor Isaev | Unwanted beam workshop 2012 | 17 -18. 12. 2012 | Seite 8
