Recent drag rate measurementsRecent drag rate measurements

Recycler Departmental MeetingNovember 8th, 2006

L. Prost, S. Shemyakin

2

Data takenData 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 hourDrag rates ranged from 25 to 50 MeV/C per hour

0

10

20

30

40

50

60

0 50 100 150 200 250 300 350 400 450 500 550

Electron beam current [mA]

Dra

g r

ate

[MeV

/c p

er h

]

2/1/2006 'Older' 6/15/2006 11/01/06 'Realigned' 11/01/06 SPB01I = 14.5 A

All but 6/15/06 data were taken with R38 <4>

4

Comparison to current density profile: Better agreement ?Comparison to current density profile: Better agreement ?

20

25

30

35

40

45

50

55

0 50 100 150 200 250 300 350 400 450 500

Electron beam current [mA]

Dra

g r

ate

[M

eV/c

per

ho

ur]

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Cu

rren

t d

ens

ity

[A c

m-2

]

R38 <4> data R111 dataJ on-axis (from scraper measurement) J on-axis (from magnetic field measurements)

Unexplained discrepancy (?!?!)

Otherwise, good agreement between the two detectors

5

Data may not be straightforward to interpret because of a Data may not be straightforward to interpret because of a wobbling energywobbling energy

-3

-2

-1

0

1

2

3

4

25 35 45 55 65 75 85

Time [min]

y-P

osi

tio

n @

R01

[m

m]

Wei

gth

ed a

ver

age

[M

eV/c

]

4.310

4.313

4.315

4.318

4.320

4.323

4.325

4.328

Pel

letr

on

vo

ltag

e [M

V]

Weighted Average YR01 YR01 'averaged' GVMVLT

Pbars ‘drift’ before the jump

6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

1 1.5 2 2.5 3 3.5

Time. hr

dU

, d

E,

kV

dU

dE

Slow (~6 minute period) energy oscillations are observedSlow (~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

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Taking advantage of the oscillations as an ‘independent’ Taking advantage of the oscillations as an ‘independent’ measurement of the drag rate for small deviationsmeasurement of the drag rate for small deviations

Pbar momentum oscillations measured on 2-Nov-2006 and simulated with a linear drag force and electron energy estimated from BYR01S position

1 1.5 2 2.5 3 3.51.8

2

2.2

2.4

2.6

2.8

3

3.2

Time, hrs

Mom

entu

m d

evia

tion

, M

eV/c

The blue curve shows the evolution of the pbar momentum Pi predicted from BYR01 positions Yi as

)]0([0 11 YYDPPP iii where P0 - initial momentum offset = 33 hr-1 - drag rate coefficientD - 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

25

27

29

31

33

35

37

39

41

43

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Momentum deviation calculated from R01 jump [MeV/c]

Dra

g r

ate

[MeV

/c p

er h

ou

r]

Modified file 806 File 806 Model ('fudged' from 02/06/06 fit)

Energy jumps calibration/uncertaintiesEnergy jumps calibration/uncertainties

Intended jump

(3.67 MeV/c)

100 mA, on axis

380 V

Error on jump (1) = 0.23 MeV/c

GVMVLT gives 0.11 MeV/c for 1

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Summary/Conclusions/QuestionsSummary/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)

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Summary/Conclusions/Questions (cont’)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 (1)

• Based on GVMVLT data, the estimated error is ~half the one calculated with position data

– But it is less sensitive

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Not a real plan but…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