1Chandra Bhat

Operational improvements to pbar

mining in Recycler

Chandra BhatRecycler Department

B. Chase and P. Joireman, RF GroupC. Gattuso, Run Co. Group

All Experimenters Meeting April 9, 2007

2Chandra Bhat

Pbars are extracted from the Recycler for Tevatron shots using longitudinal momentum mining. implemented Feb. 20, 2004

The mining is accomplished by RF manipulations of the beam using Recycler barrier rf buckets.

3Chandra Bhat

Phase-space distribution of pbars in the RR

Barrier Bucket & Beam In the bucket

Frequency Spectrum

Pbars cooled using E-cooling & Stochastic cooling

11sec

Dense region of the phase space

E0-E

E0+E

E0

Wall Current Monitor (WCM) signal

t

V

Dense region of the phase space

E0-E

E0+E

E0

Wall Current Monitor (WCM) signal

t

V E0-E

E0+E

E0

E0-E

E0+E

E0

Wall Current Monitor (WCM) signal

t

V

Synchronous

Particles

Cold Beam

High momentum

tail

RF wave form

WCM data of pbars

4Chandra Bhat

Longitudinal Momentum Mining in the Recycler

RF Waveform

WCM Dataof pbars

~300E10 pbarLE(initial)=67 eVse_T = 5 pi-mm-mr

||Mini

)10(

T

END

0.9

Before Mining

After Mining

~300E10 pbar21-38E10 pbars/mini-bunchLE=6.0 eVs/mini-bunch e_T= 5 pi-mm-mr10E10pbrs in HM bkt

||Mini

)10(

T

END

0.7-1.2

2.5sec36bkts

6.1 sec

11sec (588 bkts )

<10.25eVs

These RF manipulations take ~170 sec.

V (

kV)

2.5sec36bkts

6.1 sec

11sec (588 bkts )

<10.25eVs

These RF manipulations take ~170 sec.

V (

kV)

Bucket Area=71eVs

(Reserved for particles in the tail region)

9-Mining mini-buckets

Goal: Extract equal intensityEqual emittance pbars

Physics and first demo of long. momentum mining: C. M. Bhat, Phys. Lett. A 330 (2004) 481

5Chandra Bhat

Issues

Poor Life-time and transverse emittance growth during mining caused by non-optimal tunes

Large peak density at low emittances and higher intensities caused by hard mini-barriers

About 20% longitudinal emittance growth during the formation of four 2.5 MHz bunches for Tev shots

non-adiabatic bunch explanation Distortions of the Recycler fan out signals

due the HLRF amplifiers (Solved by adaptive RF Corrections since Oct. 2006, by Nathan Eddy, et al, All experimenter’s Meeting, Feb. 26, 2007)

Beam becoming unstable at higher stash sizes and low emittances due to resistive wall instability (Solved by use of Transverse Dampers since Aug. 23, 2005, by J. Crisp, et al. )

Made improvements in all of these with a goal of reaching the Recycler stash size of >600E10 pbars

6Chandra Bhat

R:SHLIFE =112 hrD=2.12 (xE10/mm/eVs)

1. New tune operating pointssince Aug. 22, 2006

(A. Burov, et al. from a theoretical study)

R:SHLIFE =2000 hrD=1.31 (xE10/mm/eVs)

Result: Nearly constant transverse emittance pbars to the Tevatron

Average Trans. Emit. Variation > 200%

and an RMS spread of 30%

Average Trans. Emit. Variation ~ 30%and an RMS spread <10%

V

H

RR-Beam

V

H

RR-Beam

Store=4915Old Tunes

(0.414, 0.422)

Store=4917New Tunes

(0.456, 0.465)

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2. Issues with hard Barriers

Peak particle density is too high.

RF Voltage modulation

RF Phase-modulation phase modulation can coherently perturb the particle motion.

)cos(100 maVV

Conclusions:The rf voltage and phase modulations are detrimental to the beam stability in back to back barrier buckets.

t

In 50 sec

2kV

In 50 sec

2kV

K. Y. Ng, PRSTAB, V9, 064001 (2006)

2kV

50min, 1029.2

4

pks E

eV

V

Lead to beam losses from the bucket boundary

8Chandra Bhat

Implement Soft-mining buckets

Replaced the 9-mining buckets from

0.7s

2kV

0.7s

0.2s

2kV

-0.02

0.02

0.06

0.1

0.14

0.18

0.22

0 2000 4000 6000 8000 10000

Time (nsec)

Pu

lse

He

igh

t (a

rb. u

nit)

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0 2000 4000 6000 8000 10000

Time (nsec)

Pu

lse

He

igh

t (a

rb. u

nit)

RF Waveform

WCM data

Reduced peak

density

E1/2=8.34 MeVE1/2=10 MeV

~ 25% drop in peak intensity~ 15% drop in rms energy spread

For e-cooled beam the peak density is larger

E1/2=8.34 MeVE1/2=10 MeV

~ 25% drop in peak intensity~ 15% drop in rms energy spread

For e-cooled beam the peak density is larger

Mining looks like

Expected:Since Nov. 30, 2006

Hard mini-bucket Soft mini-bucket

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Before and After Soft-mining

Peak intensity got reduced by 35%

5097 Hard mining 5123

Soft-mining

V

H

RR-Beam

Peak Intensity

V

H

RR-Beam

Peak Intensity

10Chandra Bhat

3. 2.5 MHz pbar bunches by Morphing

Before March 20, 2007

Stretch 2.5 MHz BunchesMini-bunch after mining

20-30% longitudinal emittance growth; takes ~75 sec

0.7s

2kV

2.1s

2kV

2.1s

2kV

0.7s

2kV

0.7s

2kV

2.1s

2kV

2.1s

2kV

2.1s

2kV

2.1s

2kV

Capture in 7.5 MHz 2.5 MHz Bunches

Since March 21, 2007

Mini-bunch after mining <10% longitudinal emittance growth and takes ~60 sec

0.7 s

2kV2kV

0.7 s

2kV

0.7 s

2kV2kV2kV

2.1s

2kV

2.1s

2kVMorph

11Chandra Bhat

Pbar bunches for Tev shots by Morphing for 3rd transfer

RF Waveform

WCM Data

Extractionregion

Extraction Reg.

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Accomplishments

Peak density is reduced by ~35%. – So, in future we can increase the

bunch intensity Better LE (<10% growth) pbar

bunches to the Tevatron The bunch by bunch transverse

emittance variation is reduced from 200% to 30%

With the adaptive RF correction we can send nearly equal intensity pbars bunches to Tevatron

The bunch-to-bunch luminosity variations in the Tevatron were routinely factors of 2-3. Sometimes >5.Recently, the luminosity variations are only 20-25%,

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0

1

2

3

4

5

6

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35

01

234

567

89

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35

Tevatron Bunch-by-bunch Luminosity variation PAST and PRESENT

Store 4915Without improvements:Luminosity variation >200%

Store 5306 With Improvements: Luminosity variation <15%

PAST

PRESENT

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Backup

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Current performance

Coalescing Efficiency versus Store Number

0.75

0.8

0.85

0.9

0.95

1

4700 4800 4900 5000 5100 5200 5300 5400

Soft MiningHard Mining2.5 MHz bunch by Morphing

Peak Luminosity versus Store Number

50

100

150

200

250

300

4700 4800 4900 5000 5100 5200 5300 5400

Soft MiningHard Mining2.5 MHz bunch by Morphing

MI 8GeV LE (eVs) versus Store Number

0.6

1

1.4

1.8

2.2

4700 4800 4900 5000 5100 5200 5300 5400

Soft Mining

Hard Mining

2.5 MHz bunch by Morphing

Highest peak luminosity

store (5245)

16Chandra Bhat

Adaptive RF Corrections Nathan Eddy, et al (All experimenter’s Meeting, Feb. 26, 2007)

Before RF correction Store 5007

020406080

100

1 4 7 10 13 16 19 22 25 28 31 34

Bunch Number in Tevatron

Bu

nch

In

t (x

E10

)

After DC adaptive RF correction Store 5267

020406080

100

1 4 7 10 13 16 19 22 25 28 31 34

Bunch Number in Tevatron

Bu

nch

In

t (x

E10

)

Distortions of the Recycler fan back signals were leading to Bunch intensity variation >200% & RMS intensity spread ~25%

Developed a FPGA based adaptive RF correction system.

Result: Bunch intensity variation >33% & RMS intensity spread ~6%