# Presentation: 801191

## Where we’ve been,  Where we are, & Where we’re going:

**Protons on Target**** †**** (p/cycle):****	****3.2**** ********10****12 ****	**** ****3.8**** ********10****12****	**** ****5.0**** ********10****12 **
**Cycle Time (sec):****	****2.4****	****3.2****	****1.5**
**Production Efficiency**** ****(********p/10****6 ****p ):****	****15****	****10****	****20****	**
**Stacking Rate (10****10********p/hour):****	****7****	****4****	****18**

**Where we’ve been,  ****Where we are****, & Where we’re going:**

**†**** **As read out on M:TOR109

- S. Werkema

- December 14, 2000

**Notes:**
Note:

## Why is the present stacking rate lower than Run Ib?

_**Cycle time**_** limited stacktail cooling / core cooling issues**
- When these are fixed, there is a factor of at least
- 	3.2sec/2.4sec = 1.3 to be gained in the stacking rate
- 	The hope is that the cycle time can be as low as 1.5 sec
**The **_**Production Efficiency**_** is down due to:**
- AP1 - Target Station - AP2 alignment issues
- AP2 Aperture
- AP2 - Debuncher match (or lack thereof)
- Debuncher Aperture
- Combined effect:****p yield into Debuncher 10/15)  Run Ib
- 		= 67%  Run Ib
- 	_*Or*_, Stacking rate is a factor 1.5 lower due to these problems

## Improvements / Fixes installed during November - December 2000 Shutdown

**Stochastic Cooling improvements**
- Debuncher Cooling Bands 3 & 4
- 3.2 GHz wave mode fix
- Stacktail noise floor fix
**Beamline improvements**
- Roll corrected on AP1 line Dipoles
- Installation of new Debuncher Injection Septum
**Target Station improvement**
- Lithium Lens motion control restored

## Expected stacking improvement from Debuncher Cooling improvements

**Bandwidth increased by 2******
**Gain increased by 2******
******(Depends on improvements that will be installed in early 2001)**
**Two-fold impact on stacking rate:**
**) Cooling rate in Debuncher increased by 4******
**	**_**Note**_**: *****This does not translate into a stack rate improvement***
***	****** ******until the cycle time is lowered***
**) ********p/p of********p’s injected into Accumulator is 4******** smaller **
**********Smaller ARF1 Bucket Area Required**
**	********Lower Stacktail gain required**

**Notes:**
Show next slide to explain impact of smaller dp/p
Smaller dp/p -> smaller RF bucket required
-> Smaller dp needs to be swept clear by stacktail cooling before the next pulse arrives
-> Can lower stacktail gain
-> Greater margin to instability

## Accumulator Stack Profile During Stacking

- Beam arrives on injection orbit from Debuncher
- Beam is moved with ARF1 to central orbit
- Stacktail cooling must “sweep” the new beam off the central before the next pulse arrives
- The p that must be cleared is twice the ARF1 bucket hight:

**Notes:**
Use this slide to introduce the 2.6 GHz instability

## Accumulator Cooling Issues - 2.6 GHz Stacktail Instability

**The stacktail cooling drives the beam at 2.6 GHz**
**This causes the core to oscillate coherently at 2.6 GHz**
**This coherent oscillation is detected on the core momentum cooling and the stacktail pickups**

**At high enough gain there is positive feedback via the path: **
**ST kicker **** core **** ST pickup**
**Presently this begins to happen at stack sizes of ~40mA**
**This limits the stacktail gain**** **
**This will likely force us to use the 4-8 GHz momentum system for core momentum cooling.**

**Notes:**
Show Paul Derwent’s slide #7

Feedback via beam + 2-4 GHz core momentum cooling
Show Paul Derwent’s slide #8

## Accumulator Cooling Issues - 3.2 GHz Microwave Mode

**This mode prevents use of the stacktail ********-kickers**
**The consequence of this is uncorrected heating of the core by the stacktail system**
**As the stack grows the heating gets worse requiring lengthening of the cycle time to allow the core cooling more time to work**

## Core 2-4 Schottky Signals

- No injected beam
- Stacktail ON!

**Paul Derwent**
**Slide #7**

**Notes:**
Core 2-4 GHz momentum pickup
Center = harmonic of revolution frequency
Core betatron sidebands are visible in trace with stacktail off

## Coherent Beam Feedback 

**Use Stacktail FB spectrum**
**Convolute  1/********f and Gaussian Core **
**Reasonable explanation of shape**

**Paul Derwent**
**Slide #8**

## Accumulator Cooling Issues - Can the Stacktail momentum cooling stack at 20 mA/hr?

**The maximum********p flux through the stacktail is given by the slope of the momentum distribution**
**Paul Derwent’s measurements show a maximum********p flux of ~30********10****10********p /hour for stacks of up to 70 ********10****10********p **

**Notes:**
Show Paul Derwent’s slides 2 and 3

## Stochastic Stacking

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

**Stochastic Stacking**

- Using log scales on vertical axis

**Paul Derwent   Slide #2**

## Stacktail Performance

- Fit to exponential in region of stacktail (845-875 in these units)
- Calculate Maximum Flux for fitted gain shape
- Different beam currents

- Independent of Stack Size
- Max Flux ~10x stack rate

**Paul Derwent   Slide #3**

## Cooling Issues - Conclusions:

**Debuncher cooling improvements decrease cooling time by a factor of 4 **
****** ****the Debuncher is ready for a 1.5 sec cycle time**
**It is not clear the Accumulator is ready for a 1.5 sec cycle time.  Things to worry about:**
**Will the 4-8 GHz core momentum cooling be adequate?**
**Have we fixed 3.2 GHz ********wave mode?**
**Is the core transverse cooling adequate for large stacks**
**3.2/1.5 = 2.1********Stacking Rate improvement *****only***** if the Accumulator can handle it.**
**This gives a Stacking Rate of 8.5 mA/hr**

## Core 4-8 GHz Transverse Cooling

## AP1 Debuncher Issues

**Restoring AP1 - Debuncher to their ****Run Ib**** performance would yield an additional 50% increase in Stacking Rate**
**Assuming the cooling fixes work, this increase would give a Stacking Rate of ****12.8 mA/hr****†**** - this is probably a good lower bound of what will be achieved in 2001. **
**Why is yield into Debuncher less than Run Ib?**
**Changes to upstream end of AP1 - transport from AP1 to Debuncher not yet re-optimized**
**Loss of Debuncher aperture due to cooling upgrade**
**24****21 ******** mm-mrad now versus ~27****27 ******** from run Ia**
**Replacement of trim dipoles with motorized quads**
**Can’t center cooling tanks**
**†****This figure can be increased by a factor of 5.0/3.8 when 5.0********10****12**** POT is achieved**

## Efforts under way to recover and improve on Run Ib performance:

**Target Station - AP2 alignment, optimize pulsed magnet setting**
**Add trim dipoles to AP2 line**
**Match AP2 line to Debuncher lattice**** **
**~300% blowup of vertical emittance**
**Debuncher Aperture improvements**
**Motorize more quad stands (10 by summer 2001)**

**Notes:**
Show Jim Morgan’s Studies Plan Slide

## Jim Morgan 12/12/2000

**Jim Morgan 12/12/2000**

## One more thing to worry about:

- Stacking should not quench the Tevatron
-  We suggest implementing a MI abort that would be pulled when:

- RPOS in the MI is out of spec
- P1 or P2 line power supplies at incorrect setting or not properly regulating

**Notes:**
Show Dave Johnson’s P1/P2 slide