# Presentation: 697555

## Stacking & Cooling

- Paul Derwent
- Fermilab AAC Meeting
- Feb 4&5, 2003

## Handling >40 mA/hour

- Debuncher
- 2 second cycles
- Transfer to Accumulator
- 6 MeV/c 95% width
- 50 π

- Accumulator
- 2 second cycles
- 30 minutes stacking
- 20-30e10 maximum density
- Transfer to Recycler
- 10 eV-sec
- 15 π

- Rapid transfers
- Accumulator to Recycler transfers
- Every 30 minutes
- ≤ 5 minutes setup + transfer

- Recycler
- Electron & Stochastic cooling
- Stash of 5-10 e12

## Debuncher Cooling

- Cooling rate and asymptote limited by notch filter dispersion
- Cooling Time
- Prediction: 0.2 sec
- 3 measurements:
- (1.7 ± 0.3,1.4 ± 0.2,1.6 ± 0.2)
- Average:1.54 ± 0.13 sec
- Asymptotic value:
- 7.7 MeV/c 95% width
- ~5000 Notches in system
- Aligned to same frequency?
- RMS width 3 Hz
- Better delay control (<1ps level)
- New equalizers for phase dispersion

- For 2 sec 6 MeV/c

- For 1.5 sec 4.5 MeV/c

## Stochastic Stacking

- van Der Meer solution:
- Constant Flux:
- Solution:
- Exponential Density Distribution generated by Exponential Gain Distribution
- Max Flux = (W2||*E**d*)/(f0p ln(2))

- Using log scales on vertical axis

## Stacktail Design Scenario

- Goal:  90 mA/hour peak stacking rate in Accumulator
- x2 design margin above 45 mA/hour
- Accumulate for 30 minutes, transfer to Recycler
- Optimize for maximum flux, not momentum density
- Change Bandwidth & Ed
- 2-6 GHz
- 9 MeV gain slope
- Maximum flux ~ 102 mA/hour

## Specifications

- Input:
- 50 π transverse emittance
- 6 MeV/c 95% momentum width
- 2 second cycle time

- Output:
- 30 minutes accumulation time
- 5 minutes extraction
- ~4.5 minutes setup
- ~0.5 minute extraction
- 77 mA/hour average
- Extract
- 10 eV-sec
- Transverse   ~12 π

## Design Decision

- 2-6 GHz total bandwidth in parallel systems
- 2-4 GHz band
- Equivalent to current stacktail
- Utilize existing hardware
- Replace 1/2 system
- 4-6 GHz band
- New hardware
- Pickup & Kicker loops
- New design?
- Electronics
- Layout similar for both systems

**128****/****256**** Pickup **
**Loops @ -5 **
**MeV**

**Notch filter**

- 

**32****/****64**** Pickup**
**Loops @ -22**
**MeV**

**Notch filter**

**Notch filter**

**16****/****16**** TWTs**

**128****/****256**** Kicker**
**loops**

- Two Independent Systems
- 2-4 GHz
- 4-6 GHz
- With similar layouts

- A60

- A30

- Core position -52 MeV
- 4-8 GHz system

## System Parameters

|  | 2-4 GHz System
(1/2 current system) | 4-6 GHz System
To be built |
| --- | --- | --- |
| Pickup loops | 160 | 320 |
| Kicker Loops | 128 | 256 |
| Loop Impedance | 20  | 5 (current)
10 (desired) |
| Front End Noise Temperature | 125 K | 125 K |
| Cryo Amps | 8 | 8 |
| 1 Watt Amps | 8 | 8 |
| BAW Notch Filters | 3 | 3 |
| TWTs | 20 | 20 |
| TWT Power Supplies | 20 | 20 |
| Total Power | ~500 W | ~500 W |

## Simulation Results

- Stack Rate = 91.9 mA/hour
- 78.8 mA/hour including extraction time
- ~1 kW total power

## Simulation Tests

- Single Pulse Evolution
- Single pulse into Accumulator
- Using 79 MHz longitudinal Schottky, track evolution of the pulse
- Motion of the mean
- Change in the width
- Direct Comparison of simulation and current stacktail

- Frequency (Hz) -- 127th Harmonic

## Pulse Evolution

## Study Plan

- Proton Stacking:
- Test current systems to their limits
- Input Flux and System Power
- Proton flux ~6x pbar flux
- 1996 test:  Tev I design
- 12.2 mA/hour with 5 second cycle
- Simulation predicted max of ~14 mA/hour
- Under different input conditions
- Debuncher cooling rates:  longitudinal and transverse
- Accumulator Stacktail
- Test simulation matching
- Pulse evolution
- Stacking rate
- 1 Week dedicated time

## Rapid transfers

- Dec 02:  ~1 transfer to Recycler per day
- To understand mechanics of transfer
- 60 minutes from stacking to stacking
- 30 minutes setup with focus on emittance preservation:
- Positions in MI & Accumulator
- Do not do beam line tuneup
- 30 minutes for multiple transfer
- ~80% efficiency
- Plan: Continue with daily transfers
- Short term:  30 minutes stacking to stacking
- Beam quality (longitudinal & transverse)
- 200e10 stash in Recycler
- Integration into Collider operation

## Electron Cooling Test Facility at WideBand Building

- 5 MV Van de Graaff accelerator (Pelletron)
- Will be installed in MI-31
- Prototype Electron beamline
- Closely resembles final beamline
- Most will be used in MI tunnel installation

## Recycler Electron coolingProject Goals

|  | Goal | Achieved? |
| --- | --- | --- |
| Recirculated electron beam current | 0.5 A | YES |
| Electron beam kinetic energy | 4.3 MeV | YES |
| Beam angular spread (cooling section) | 80 μrad | Not yet |
| Magnetic field at cathode | 600 G | YES |
| Beam diameter at cathode | 5 mm | YES |
| Energy spread | 500 eV | Yes |
| Pressure (cooling section) | 1x10-10 Torr | Not yet |
| Recirculation stability (average) | 1 hour | NO
20 min @ 3.5 MeV
<4 min @ 4.3 MeV |
| Beam recovery time | 5 min | YES (20 sec) |
| Typical time between tank openings | 1 month (initial)
6 months (final) | YES |
|  |  |  |

## Recycler Electron Cooling Schedule

- Completed tests with short U-bend beam line
- Installation of full scale beam line, switchover in late Mar, 2003
- Signed off on construction of building to begin Mar 3, 2003.
- 11 months construction
- 6 weeks shutdown to tie in to MI tunnel (late summer, 2003)
- Installation at MI-31 (Feb-May, 2004)
- Additional down time for beamline installation and commissioning (possibly summer 2004)
- Testing will continue at WideBand in interim

## Handling >40 mA/hourWhere things stand

- Debuncher
- 8 MeV/c asymptotic width
- 1.5 second cooling time
- Improve longitudinal cooling rate to achieve desired 6 MeV/c 95% width
- High flux study with proton stacking in spring

- Accumulator
- Design to handle 90 mA/hour peak, 80 mA/hour average
- Testing simulation with measurements that can be done in current setup
- High flux study with proton stacking in spring

- Rapid transfers
- Accumulator to Recycler transfers
- 60 minutes now
- 80% transfer efficiency
- 30 minutes short term goal
- <5 minutes necessary

- Recycler Electron Cooling
- Steady progress
- MI 31 construction Mar 2003
- 11 - 12 month schedule
- 2 months shutdown for tie-in and commissioning