TWiki> SPL Web>Linac4Web>RFStructureMeetings>Minutes14November2008 (2008-11-21, SuitbertRamberger) EditAttachPDF

M. Schuh, M. Vretenar, G. DeMichele, S. Ramberger, R. Wegner, N. Alharbi

**DTL**

- First measurment results:
- TM
_{010}found at 352 MHz without waveguide couplers - first Q measurements with TM
_{010}at only ~8500 (half drift tubes are made of aluminium, no RF contact in half drift tubes) - with post couplers: measured E0, a flat field is found at certain post-coupler lengths
- First bead-pull measurment results (GiovanniDeMichele)
- all futher measurement results can be found here

- TM
- avoid to adjust field with post couplers due to higher load on coupler and lower Q
- to do measurements without post couplers: moving only tuners to adjust field (see presentation from SNS)
- in order to improve the Q factor, half drift tubes in the end-caps should be welded in; for Q factor measurements additional end-plates with copper plated half drift tubes may be envisaged
- for power measurements water cooled end-caps are required
- perform high power test (LINAC4 duty cycle) without post couplers at CERN:
- Measure X-Rays (
**action**: contact safety staff) to estimate field levels - test with magnets in drifttube

- Measure X-Rays (
- SPL duty cycle as 2nd priority, there might be heat problems with the actual setup and a irreversible deformation should be avoided

**PIMS, thermal drifts**

- during operation with SPL duty cycle, PIMS modules will heat up considerably, the frequency will decrease of about 200kHz (worst case)
- if for any reason, one cell will get a small frequency offset, the power distribution within a PIMS module will change in a direction that will amplify this frequency offset and again the power distribution will change. Is this a drift (convergence) or an instability (divergence)?
- the strongest effect will occur for a frequency offset in one end cell. So assuming an initial frequency offset of
*df*= +10 kHz in one end cell,_{0} - the power in this cell will fall down to
*p*= 99.2% of the nominal power level (more power will be dissipated in the other cells, the total power level is assumed to be constant all the time)_{1} - as the power of the end cell is reduced, it cools, shrinks and its frequency increases further, in numbers, to
*df*= +11.57 kHz_{1} - again the power drops, to and the frequency increases to
*df*= +12.09kHz_{2} - after the nth iteration, the frequency offset will be with in the case of the PIMS hot prototype
- as q<1, we have convergence and the final frequency offset is . Plot thermal drift df
- curves show the relation between the initial frequency offset and the final frequency offset for each of the 7 PIMS cells. Furthermore, the Tilt sensitivity and max-min/mean voltage errors including the discussed drift effects are given for frequency offsets in each cell. Plot thermal drift Verr -- (RolfWegner)

-- MarcelSchuh - 20 Nov 2008

I | Attachment | History | Action | Size | Date | Who | Comment |
---|---|---|---|---|---|---|---|

First_bead-pull_DTL.pdf | r1 | manage | 185.2 K | 2008-11-20 - 10:43 | MarcelSchuh | ||

eps | thermal_drifts_Verr.eps | r1 | manage | 21.3 K | 2008-11-20 - 10:47 | MarcelSchuh | Plot thermal drift Verr |

eps | thermal_drifts_df.eps | r1 | manage | 21.3 K | 2008-11-20 - 10:46 | MarcelSchuh | Plot thermal drift df |

Topic revision: r4 - 2008-11-21 - SuitbertRamberger