# Presentation: 519866

## Debuncher Muon Source at FermilabUpdate

- David Neuffer
**Fermilab**

##  New Scenario overview

- Protons from Booster injected into Accumulator
- Stack 1 to 6 booster turns, debunch
- ~5·1012 nturns protons
- L = nturns 8 eV-s
- Rebunch
- to ~40ns rms single bunch
- Takes 0.1 to 0.2 s
- Could be done in Accumulator ??
- Extract into Debuncher
- Complete rebunching
- Slow extract to muon conversion experiment
- over ~1.33s

**Booster**

| Parameter | Symbol | Accumulator | Debuncher |
| --- | --- | --- | --- |
| Circumference | C=2πRave | ~454m | 504m |
| Momentum | P | 8.89 GeV/c | 8.89 GeV/c |
| Transition  | γT | 5.4 | 7.52 |
| betatron fns | βx, βy, η m | 47, 40, 9.6 | 19.8, 17, 2.2 |
| Tunes | νx, νy | 6.9, 8.9   | 9.65, 9.76 |

## MI 1.33sec=20 Booster Pulses

**There will be up to 6*5x10****12****protons per 1.33sec ~2.2x10****20**** per year**

## Momentum stacking in Accumulator

- Up to 6 batches ??

## Longitudinal stacking in the Accumulator 

**Longitudinal stacking in the Accumulator **

- ΔEfull = 20 MeV

## Beam requirements for ~MECO

- Bunch beam to a fraction of the debuncher circumference
- < ~200ns of 1700ns
- Keep beam leakage outside that bunch length to a minimum
- Debuncher timings similar
- 	to MECO/BNL
- But longitudinal emittance larger
- <10 eV-s  ~8 Nturns eV-s
- Develop most effective/efficient
- 	bunching scheme
- barrier bucket?
- multiharmonic?

- MECO/BNL running cycle

## Larger Emittance 4 -> 6 batches

- Emittance of proton beam is Nbatches8 eV-s
- 4 batches is 32 eV-s
- 6 batches is 48 eV-s
- + dilution
- Can bunch 6 batches
- Requires ~2  Vrf as 4 ...
- With L = 48 eV-s, E = 300 MeV, T  > 160 ns
- Longer bunch length reduces duty cycle

## Barrier Bucket Bunching parameters

- Barrier bucket: 30kV, 40o
- 0.135s transition time
- H=4 rf (2.367MHz   50150 kV)
- 0.05s ramp/bunching time
- Hold at 150 kV
**Beam is bunched to  10o**, σE **=60 MeV**
**ε****L**** = 47.5 ******** 52.8 eV-s emittance growth**
**Corresponds to ~ 6 booster turns**
**Requires ~2× rf as 4-batch bunching **

## Barrier bucket bunching- 

## 4-Harmonic parameters-6 batch

- 4 harmonics
- h=1: 0 to 8 to 38 kV; h=2:0 to 4 to17 kV, h=3: 0 to 2.7 to 12kV
- 0.0323s
- h=4 :60 to 125 kV
- Emittance increases from 47 to 52 eV-s
- Faster bunching than barrier bucket case ...
- ~0.2s is reduced to ~0.05s
- Scenarios assume gap formed in Debuncher and transfer to accumulator

## 4-harmonic buncher

## Can bunch in Accumulator Instead ...

- If accumulator and debuncher are both used in  2 e
- NOT  USED FOR SNUMI  ??
- Bunching time does not count against experiment time
- Bunching time (0.3s) then does not count against slow extraction time (<1.33s)
- Less isochronous (more Vrf but shorter bunching time)
- Similar schemes with more rf required.

## Hybrid scheme 

**Accumulator **
- Momentum stack 1 to 6 booster batches
- Adiabatically bunch at h=1- **4kV**
- 500ns gap for kicker
- Some beam/halo cleaning in Acc and transfer
- Adiabatic easier at T=5.5
- Transfer to Debuncher
**Debuncher**
- h=1 90-degree phase rotation at fixed voltage
**40kV** - 0.007s
- Capture and store at h=4
- ~**200** to 250 kV ~0.02s;   = 42ns fairly long bunch
- Beam halo cleaning also  ....

## Bunch, Rotate, Store scenario

## Comments on Hybrid scenario

**Adiabatic bunching is better in Accumulator**
**Phase-Energy rotation better in Debuncher**
**Uses only h=1 and h=4 rf**
**Rf voltage requirements relatively modest**
**Could be improved using some higher harmonics**
**Do not need separate extraction gap formation in Accumulator**
**Extraction gap formed by h=1 adiabatic buncher**
**Gap > 500ns; transfer kickers are correspondingly easier**
**Beam Halo clearing in Accumulator possible**

## Space Charge Limit

- Space Charge tune shift:
- Parameters: Ntot=31013,εN =20π mm-mrad
**~Debuncher Ring: 1 bunch, 100ns/1.7****μs** :        BF= 0.059
- →δν = ~ 0.20: not too large??
- Intensity limit?

## Needed to develop concept:

- Longitudinal bunching scenario
- Develop optimum
- Injection/Extraction lines
- Slow extraction line to target
- Location of mu-e detector
- Extinction
- Is full width ~200ns short enough?
- Favors Al target
- Smaller value means stacking fewer Booster batches
- calculations/methods/improvements