Recent%20drag%20rate%20measurements - PowerPoint PPT Presentation
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Recent%20drag%20rate%20measurements
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Title: Electron Cooling Commissioning Update Author: Beams Division Last modified by: Beams Division Created Date: 4/19/2005 9:06:55 PM Document presentation format – PowerPoint PPT presentation
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Title: Recent%20drag%20rate%20measurements
1
Recent drag rate measurements
- Recycler Departmental Meeting
- November 8th, 2006
- L. Prost, S. Shemyakin
2
Data taken
- Drag rate measurements with the electron beam on
axis, 2 kV jumps - 100 mA 400 mA
- Nominal file (806)
- Magnetic field realigned recently
- Modified file 806
- SPB01I changed from 13.5 A to 14.5 A
- From focusing optimization based on equilibrium
changes of a cooled beam at 200 mA (1 mm offset) - Equilibrium to equilibrium
- Check old SA calibration
- Got unexpected data due to slow energy
oscillations - Additional output
- Energy vs y-position at R01
- Jumps calibration
3
Drag rates ranged from 25 to 50 MeV/C per hour
All but 6/15/06 data were taken with R38 lt4gt
4
Comparison to current density profile Better
agreement ?
Unexplained discrepancy (?!?!) Otherwise, good
agreement between the two detectors
5
Data may not be straightforward to interpret
because of a wobbling energy
Pbars drift before the jump
6
Slow (6 minute period) energy oscillations are
observed
- Comparison of the Pelletron voltage variation dU
recorded with GVM and the electron energy
variations dE calculated from BYR01S - Both signals are averaged over 30 sec
- Calibration from a jump (last week presentation)
- 0.31 mm/kV
- Source of these oscillations is unknown
- Voltage regulation loop ?
- Temperature ?
This is a new observation
7
Taking advantage of the oscillations as an
independent measurement of the drag rate for
small deviations
- The blue curve shows the evolution of the pbar
momentum Pi predicted from BYR01 positions Yi as
where P0 - initial momentum offset ? 33 hr-1 -
drag rate coefficient D - coefficient
translating the dispersion in BYR01S into the
units of MeV/c per mm Y0 - beam position in
BYR01S corresponding to an equilibrium energy
8
Energy jumps calibration/uncertainties
380 V
100 mA, on axis
Intended jump (3.67 MeV/c)
Error on jump (1s) 0.23 MeV/c
GVMVLT gives 0.11 MeV/c for 1s
9
Summary/Conclusions/Questions
- Fastest drag rates ever recorded
- Max 50 MeV/c per hour for Ib 300 mA
- Better magnetic field alignment
- Better alignment with pbars
- Smaller emittances ?
- Better focusing ?
- In particular for 300 mA case
- Should not matter on axis
- May be slightly better agreement with estimation
of the dependence of the drag force with the
current density on axis - But still abnormally low drag rate for high
electron beam current (e.g. 400 mA) - Standard data analysis (shown here) may be too
simple for this set because of the energy
wobbling continuously (see following points)
10
Summary/Conclusions/Questions (cont)
- Slow and relatively large energy oscillations
were observed (with pbars and R01 position) for
the whole duration of the measurements - New phenomenon/observation
- Better (higher) drag force ?
- Temperature variations ?
- Relatively good agreement between the two
measurements using a linear model for the drag
force - Small oscillations
- Possibility to use an applied sinusoid for
automated measurement of the drag force - Continue to use R01 position as a spectrometer
- Estimated errors for the jump 0.23 MeV/c (1s)
- Based on GVMVLT data, the estimated error is
half the one calculated with position data - But it is less sensitive
11
Not a real plan but
- We want to continue (and accentuate) the
investigation of the friction force and cooling
rates - More measurements will be requested
- Visitors from BNL will come to Fermilab in
December for that purpose - Very important for their project which goes into
review in the Spring - Goals
- Improve cooling (FNAL)
- Rates, lifetime,
- Understand cooling (FNAL, BNL,) !!
- Physics contribution of the Electron cooling
project
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