# Presentation: 177790

## Current Operational Status of Recycler Ring

- Cons Gattuso
- DOE Tevatron Operations Review
- March 21, 2006

## Complex Pbar Production Chain

- The Antiproton Source is made up of three parts. The first is the Target: Fermilab creates antiprotons by striking a nickel target with protons. Second is the Debuncher Ring: This triangular shaped ring captures the antiprotons coming off of the target. The third is the Accumulator: This is the storage ring for the antiprotons.  Recently, we have added another ring, the Recycler, for additional antiproton storage.

## Recycler – 8.9 GeV/c Storage Ring

- At the end of August 2003
- The Recycler was “on the ropes”
- Lifetime was < 60hrs
- Transverse emittance growth was 12-mm-mrad/hr
- Took drastic measures
- Lengthened the Fall 03 shutdown to bake the entire Recycler
- Instituted the Pbar Tax (Investment) to guarantee the Recycler adequate study time and access to the tunnel

- Recycler bake-out was extremely successful
- Transverse emittance growth reduced by a factor of 10-20
- Lifetime > 600 hours
- Recycler commissioning has progressed rapidly
- Using the Recycler in  “Combined Shots” operations makes it a luminosity enhancement
- Operational January 2005
- Transverse Damper commissioned August 2005
- Stashes larger than 120x1010 Pbars now possible
- Stand alone Recycler shots to the Tevatron (October 2005)
- Stashes of 250x1010 Pbars in the Recycler
- Average Coalescing eff 86%
- Average Efficiency to collisions 77%
- Electron Cooling commissioned July 2005
- Starting in August 2005, electron cooling is used on every Tevatron shot.

## Recycler Electron Cooling

- The maximum antiproton stash size in the Recycler is limited by
- Stacking Rate in the Debuncher-Accumulator at large stacks
- Longitudinal cooling in the  Recycler
- Longitudinal stochastic cooling of 8 GeV antiprotons in the Recycler is being replaced by Electron Cooling
- Electron beam: 4.34 MeV – 0.5 Amps DC – 200rad angular spread
- Max beam current 730 mA Circulated in cooling section
- In U-Bend mode currents of 1500 mA has been obtained.

## Recycler-Only Operations

- With Electron Cooling operational and the transverse dampers commissioned, a Recycler stash size can now be increased to over 300x1010 Pbars
- Turn around time from last transfer is about 1.5 hrs. (time can be reduced to about 45 mins – 1 hr.)
- Transfer eff  from ACC to RR with stash sizes ~300 E10 is on the order of 90-92%
- After Recycler only shots to the Tevatron  the remaining is cooled and an additional transfers into the machine commence.
- 	( <= 1 hr.)

- The Collider complex has now transitioned from Combined Shot mode to Recycler-Only mode
- Faster average stacking
- We save about 30-45 mins of shot setup time
- Smaller Pbar emittances in the TEV
- Continue to stack Pbars in the Accumulator

## Recycler Injection Sequence

- RF Fan back

- RWM Readback

- 11sec

- Injection
-  Region

- Cold Beam
- Region

## Pbar Injection into the Recycler

- Transfer efficiencies  of > 90%
- For Stash sizes up to 300 E10

- Closure error <.1 mm

- Beam transfer into the Recycler
- Energy matching between the MI and RR(~45 MeV difference)
- Cogging to align beam markers

## Injection/Cool Down History

- Electron cooling
- prior to extraction

- Stochastic cooling
- after injection

- 	Electron cooling between transfers

## Electron cooling in operation

- Electron cooling
- prior to extraction

- Stochastic cooling
- after injection

- 200E10 Pbars with ~55 eVs
- Before Mining

- After Mining

- 6 eVs/transfer

- (4) 2.5 Mhz bunch

- RF Fan back

- RWM Readback

## Intensity Vs. Longitudinal Emitt.

**MAX**

**GOAL**

**1.5 eV s per bunch**

**2.0eV s per bunch**

**36 Bunch**
**Extraction**

## Collider Transfers

- Recycler only shots
- 79 shots to the Tevatron have occurred (Oct 5th 2005)
- Average stash that we shot from ............................220 E10
- Average intensity per transfer (4 2.5Mhz bunches)................................................................................23.0E10
- Percentage of beam captured for extraction......95-97%
- RR to MI Transfer efficiency ....................................95%
- Emittances supplied
- Transverse ...................3-6 pi mm mr
- Longitudinal ...................1-1.5 eVsecs

## Shutdown Activities

- Flying Wire upgrade
- Reduce the Carbon Fiber wire diameter from 33 to 5 microns
- Reduces transverse emittance growth allows us greater latitude in usage during normal operations.
- Damper upgrade (80 MHz Damper system)
- Shorter kickers installed at higher beta
- 		    	 _OLD_                                          _New_
- Length:      	1.4m kickers 		 .5m kicker
- Beta:         	18H/27V                           54H/55V[meters]
- 3dB Bandwidth
- Kicker: 		48 MHz		       	  135 MHz
- Switch to VME board designed for damper
- Application program with improved user interface provide more information to user separate Hor and Ver VME boards will allow sampling A+B  allows changes in gain with intensity to improve dynamic range

## Shutdown Activities

- Vacuum maintenance
- Firing of TSP’s ring wide
- Average vacuum pressure in the ring is <10 E-11
- Leak Check
- Investigate vacuum burst in the Pbar extraction line
- RF upgrade
- Modify RF amplifiers
- Adding water cooling to the amplifiers to improve reliability and the RF response as a function of time.

## Operational Gains

- Studies Shots
- to the Tevatron

## Final Recycler beam parameters

- Short term goals (*achieved*)
- Recycler provides all Tevatron Pbars
- 250x1010 Pbars  delivers 7e1010 Pbars per bunch in the Tevatron (75%  ( *77%* ) efficiency to collisions, 36 bunches)
- Mining efficiency of 90% (*95-97%* )
-  Long. emittance (95%): 54 eV-s (*55 eV-s*)
- Transverse emittances (n, 95%): 5 pi-mm-mr
- Shot with emitt range from *3-5 pi-mm-mr*
- Smallest emitt of *2.8 pi-mm-mr*
- Supports peak luminosities above 160x1030 1/(cm2s)
*	**Record Luminosity  1/6/06 store 4581   171.85 E30*
- End of Run II:
- Up to 510x1010 Pbars
*Max Stash size of 437 E10 2/14/06*
- Same emittances