Proton Beam Measurements in the Recycler

Duncan ScottOn Behalf of the

Main Injector Group

Contents

• Confirm Nova Operations Will Work– Operating the MI8 Injection line at the Recycler energy

• The MI8 line transfers beam from the booster• The RR has a slightly different energy to the MI • MI8 has many permanent magnets

– Stacking in the Recycler• Do we have enough aperture?

– What are the expected tune shifts?• Due to MI Ramp• As Intensity Increases• Due to RF Frequency Changes

• Other Experiment Example– Finding Zero Chromaticity with Schottky and BPMs

Operating MI8 Line at RR Energy

• The RR has a slightly different energy to the MI– Change Booster Energy and RF Frequency, fRF – Try to Inject into MI

• Differences between MI and Recycler – Momentum

• From 8.884 to 8.836 GeV/C– Fix the MI Dipole field at RR value and adjust Booster dipole (B:VIMAX)– Calculated change is ~4 A

– fRF

• From 52 811 400 to 52 809 000 Hz, ∆f=2 400Hz– Change MI fRF and Booster locks to that

Change B:VIMAX

Beam in Booster

B:VIMAX

MI8 Orbit

• 1st attempt beam hits MI8 collimators

• Calculate changes to horizontal trims and try again

• 2nd attempt beam is injected into MI

MI Orbit & Correction Strength• Reasonable injection and closed orbit in MI• Less current used in horizontal trim

magnets

Injection

Vertical

Vertical

Longitudinal Stability in MI

• WCM data shows stable bunches and bunch spacing– Phase is well matched

Slip-Stacking

• NOVA operations will increase the beam power through the Main Injector by a factor 2

• Previously the beam was stacked in the MI then ramped

• For Nova we will slip-stack beam in the Recycler whilst the MI is ramping– Approximately halves the cycle time

Slip Stacking• Stack Beam in Longitudinal Phase Space

– Two sets of bunches separated in azimuth and energy in 2 RF systems– They “Slip” relative to each other– Apply large voltage RF to capture 2 bunches in 1 bucket

– In the Recycler we plan to do 12 batch slip stacking. • Inject 6 Booster batches at one frequency, • Reduce that frequency• Inject 6 more batches at original frequency• Transfer to MI and Recapture

+∆f

-∆f

Recycler Requirements for 12 Batch Slip Stacking

• Different schemes can affect the amount of momentum aperture required– We could inject on momentum, decelerate, inject, accelerate

• Preferred option, centres beam in magnets, better lifetime, etc.

– Inject off-momentum, with half required ∆f, then decelerate • Requires less momentum aperture

0

-∆f

+∆f

Inject on momentum Inject off momentum

fRF

time

52MeV

40 MeV

Recycler Requirements for 12 Batch Slip Stacking

• The central frequency separation between the two beams is fixed– ∆f = 1260 Hz or ∆p =24 MeV.

• Assume Booster beam has momentum spread of ±8 MeV (95%)– The min. momentum aperture required is 40 MeV or ∆p/p = 0.45%

24 MeV

10.2 MeV

95 KV Bucket

95 KV Bucket

8 MeV

40 MeV

Measured RR Momentum Aperture• Change RF

frequency and measure beam transmission

• This will need to be remeasured– Currently

equipment is being removed, Lambertsons, E-Cool, etc.

– This should only increase the aperture

> 99% Transmission∆p/p =0.45 %

> 95% Transmission∆p/p =0.65 %

Minimum∆p/p required

H Chrom = +3.0V Chrom = -4.6

Tune Change with MI Ramp

• The Ramp of Magnets in MI will affect the RR tune

• Tune measured from BPM data taken after beam is pinged

• Time of ping varied over eventKicker firing at

different time in cycle

Tune Change vs MI Ramp

• Tends to follow rate of change of momentum (pdot)• Faster ramp may increase ∆Q ?

Max ∆Q=0.005

Tune Change with Intensity• Measured tune for different intensity beams in

MI • Line is theory (B. Ng)

• From Batch 1 to 6 Max ∆Q=0.01

ΔQh=−1.1410−4 𝑁𝑏

𝜏+6.91510−6𝑁 𝑏𝑀

ΔQ v=−1.3910− 4 𝑁𝑏

𝜏−7.18410− 6𝑁𝑏𝑀, , , bunch length (ns)

Tune Change with fRF

• Tune measured with Schottky, for low chromaticity, Hchrom=+3, Vchrom=-4.6

• Change at High Chromaticity (-17) measured in MI

Max ∆Q=0.04

Zero Chromaticity Measurementswith Schottky

• Width of Schottky signal measures chromaticity – Minimum width is zero chromaticity

• How does measured 0 Chrom. compare with “Set” 0 Chrom ?

• Saved Scope images whilst changing Chrom

• Extract coordinates

• Fit Gaussian• Find min

width

Zero Chromaticity Measurements with BPMs

• Measured Qv vs ∆fRF for different Vchrom settings

• Plot gradient of each VChrom setting

• Zero gradient = Zero Chromaticity, at Vchrom=-0.38

• (-0.75 from Schottky)

Conclusions

• Successfully Operated MI8 Line at RR Energy– MI8 line works better with RR energy– Energy matching worked second attempt, phase matching first attempt

• Verified the RR has the Min. Aperture Required– Slip stacking requires momentum aperture, between 40 and 52 MeV– Measured aperture is at least 40 MeV– Should only increase after Lambertson E-Cool removal, etc.– Re-measure after shutdown

• Measured Tune Changes that Need Compensating– 0.005 with MI Ramp– 0.01 with intensity, from batch 1 to 6– 0.04 for RF changes (at high chromaticity)

• Other Experiments for Fun and Learning

Thanks

• Ming-Jen Yang• Denton Morris• Ioanis Kourbanis• & Operations