Booster Operation in Support of the Collider Program

Eric Prebys
Accelerator Technology Seminar, March 18, 2003

Control and Instrumentation

Every long and short section (2x24=48) has

A horizontal and vertical BPM

Can read out turn by turn for two or 50 time points for all 96

A beam loss monitor

Can snapshot all 96 for each cycle

Horizontal and vertical trims

Originally DC. Working on active control for the 24 high-b ones in each plane.

Quads and Skew Quads

Each has an individual DC setting plus common ramp.

Chromaticity sextupoles controlled by ramps

Some individual loss monitors at key locations.

Horizontal pinger for tune measurement

Couples to V plane

Doesn’t work at the moment (had to steal kicker)

8 GeV Proton Run II Goals and Performance

The “Run II Era”

The proton source is very close the the specifications in the Run II Handbook.

Although it’s the highest priority, support of collider operations is a relatively minor facet of life in the proton source.

Proton source activities are dominated by the current and projected needs of the neutrino program (MiniBooNE+NuMI+??)

Whatever a WBS chart may say, there’s not a separate proton source for RunII, MiniBooNE, NuMI, etc.

Demand for 8 GeV Protons

Where do Protons Go Now?

Limitations to Total Booster Flux

Total protons per batch: 4E12 with decent beam loss, 5E12 max.

Average rep rate of the machine:

Injection bump magnets (7.5Hz)

RF cavities (7.5Hz, maybe 15 w/cooling)

Kickers (15 Hz)

Extraction septa (was 2.5Hz, now 15Hz)

Beam loss

Above ground:

Shielding

Occupancy class of Booster towers

Tunnel losses

Component damage

Activiation of high maintenance items (particularly RF cavities)

Typical Booster Cycle

Proton Timelines

Everything measured in 15 Hz “clicks”

Minimum Main Injector Ramp = 22 clicks = 1.4 s

MiniBoone batches “sneak in” while the MI is ramping.

Cycle times of interest

Min. Stack cycle: 1 inj + 22 MI ramp = 23 clicks = 1.5 s

Min. NuMI cycle: 6 inj + 22 MI ramp = 28 clicks = 1.9 s

Full “Slipstack” cycle (total 11 batches):

6 inject
+ 2 capture (6 -> 3)
+ 2 inject
+ 2 capture (2 -> 1)
+ 2 inject
+ 2 capture (2 -> 1)
+ 1 inject
+ 22 M.I. Ramp
----------------------
39 clicks = 2.6 s

Summary of Proton Ecomomics

Time Line Issues

The Time Line Generator (TLG) sequences all accelerator operations.

Traditionally, each sequence (“module”) is independent, including any necessary Booster prepulses.

This wasn’t really compatible with the goal of getting the maximum possible beam out of the Booster.

In the new scheme:

Standalone sequences are placed in the time line, with necessary prepulses

MiniBooNE pulses are “trailer-hitched” to the end of these to achieve a specified average repetition rate, subject to an overall total rate.

If there aren’t enough modules to trailer-hitch to, new modules will be built (still working the bugs out of this one).

Booster Losses (Normalized to Trip Point)

Booster Tunnel Radiation Levels

How Have We Been Doing?

Some Cold Hard Facts about the Future

Running as we are now, the Booster can deliver a little over 1E20 protons per year – this is about a factor of six over typical stacking operations, and gives MiniBooNE about 20% of their baseline.

NuMI will come on line in 2005, initially wanting about half of MiniBooNE’s rate, but hoping to increase their capacity – through Main Injector Improvements – until it is equal to MiniBooNE.

Whatever the lab’s official policy, there will be great pressure (and good physics arguments) for running MiniBooNE and NuMI at the same time.

-> By 2006 or so, the Proton Source might be called upon to deliver
10 times what it is delivering now.

At the moment, there is no plan for assuring this, short of a complete replacement!

So what are we going to try?…

Some Things Which Have Been Done

Shielding and new radiation assessment

Vastly improved loss monitoring.

New (MP02) extraction septum and power supply (enable high rep. rate running)

New tuning strategies.

Booster Collimator System

Unshielded copper secondary collimators were installed in summer 2002, with a plan to shield them later.

Due the the unexpected extent of the shielding and the difficulty of working in the area, the design was ultimately abandoned as unacceptable.

Collimators were removed during the January shutdown.

A new collimator system is being designed with steel secondary jaws fixed within a movable shielding body.

Hope to have then ready before summer shutdown.

New Collimator System

New RF System?

The existing RF cavities form the primary aperture restriction (2 ¼” vs. 3 ¼”).

They are high maintenance, so their activation is a worry.

New RF System (cont’d)

There is a plan for a new RF system with 5” cavities:

Powered prototype built

Building two vacuum prototypes for the summer shutdown with substantial machining done at universities.

Evaluate these and procede (hopefully?) with full system.

Total cost: $5.5M cavities + $5.5M power supplies (power supplies would pay for themselves in a few years)

Is it worth it? On of the questions for the study group is how much improvement we might expect.

Injection Dogleg (ORBUMP)

The current injection bump dogleg (ORBUMP) magnets can ramp at 7.5 Hz, with a substantial temperature rise.

Need to go to 10 to support MiniBooNE and NuMI.

2 spares for the 4 (identical) magnets. Most likely failure mode probably repairable.

Considering new design which will stretch existing magnets further apart, which will lower their current, but will require a pulsed injection septum between the first two.

Can new design incorporate injection improvements??

Some power supply issues as well:

One full set of replacement SCR’s for the switch network.

New switchbox being designed, but needs attention (or order more spare SCR’s).

No spare for charge recovery choke.

Multibatch Timing

In order to Reduce radiation, a “notch” is made in the beam early in the booster cycle.

Currently, the extraction time is based on the counted number of revolutions (RF buckets) of the Booster. This ensures that the notch is in the right place.

The actual time can vary by > 5 usec!

This is not a problem if booster sets the timing, but it’s incompatible with multi-batch running (e.g. Slipstacking or NuMI)

We must be able to fix this total time so we can synchronize to the M.I. orbit.

This is called “beam cogging”.

Active cogging

Detect slippage of notch relative to nominal and adjust radius of beam to compensate.

Simulation/Studies

Historically, the booster has lacked a fundamental understanding of beam loss mechanisms.

If (!!!) it is possible at all to go the the required beam flux, it will require some mitigation of beam loss.

Recently, there has been an great increase in the involvement of the Beam Physics department in the Booster:

Space charge group (W. Chou, et al) has begun to focus on the Booster again.

Chuck Ankenbrandt has moved into Booster group as “Beam Physics Liaison” to help coordinate studies.

Starting to make quantitative comparisons between predictions and measurement.

An almost immediate result of this increased effort was the discovery of the “dogleg problem”….

Dogleg Problem

Parasitic Focusing

Parasitic Focusing (cont’d)

Predicted Effect of Doglegs

Preliminary Study: Dispersion

Dead Dog Studies

Took advantage of recent TeV Magnet failure to raise the Long 13 (dump) septum and turn off the associated dogleg.

Doglegs almost exactly add, so this should reduce the effect by almost half.

The mode of operation prevents short batching, booster study cycles and RDF operation.

Had about 36 hours of study in this mode.

Bottom Line: major improvement.

Transmission After Tuning

Transmission with One Dogleg

Record Running w/o Dogleg

Short Term Solutions

Tune to minimize current?

helped so far, but near limit.

Maybe raise L13 septum a bit?

Motorize L13 septum to switch modes quickly?

Operational nightmare

Eliminate L13?

Find another way to short-batch

Make a dump in MI-8 for Booster study cycles?

Correctors?:

These don’t look like quads, so can’t find a fix – yet.

Spread out doglegs (effect goes down with square of separation):

Not a lot of room. Maybe separate downstream magnets?

Three-legged dog?

Turn of the third of the four magnets.

Need to increase first two reduces net improvement.

Long Term Solutions

Large Aperture Lattice Magnets?

Obviously the “right” idea.

Must match lattice AND (preferrably work with existing resonant circuit).

Potential for big screw-up.

Pulsed extraction bump?

Straightforward magnet design.

Only part of the lattice for a short period at the end of the cycle.

New ideas welcome.

Longevity Issues (non-radiation)

GMPS (upgraded, OK)

Transformers (serviced, OK)

Vacuum system (being updated, finished 2003)

Kicker PS charging cables

Run three times over spec

Evaluating improved design (better cable, LCW-filled heliac, etc)

Low voltage power supplies, in particular Power 10 Series:

Unreliable, some no longer serviced.

Starting search for new supplier and evaluate system to minimize number of different types.

Probably a few $100K to upgrade system.

Longevity Issues (non-radiation, cont’d)

RF Hardware

(original) Copper tuner cooling lines are beginning to spring leaks. Difficult to repair because they’re hot.

High Level RF

More or less original.

Our highest maintenance item.

Will probably last, BUT expensive to maintain.

John Reid and Ralph Pasquinelli feel a new solid state system would pay for itself ($5.5M) in about four years.

Low Level RF

Many old modules, some without spares, some without drawings.

An upgrade plan in place.

Not expensive, but NEED people.

Personnel!!!!

Radiation Damage Worries

Cables: frequent replacement of HV cables and connectors for ion pumps.

Hoses: valve actuator hoses have failed and are now being replaced with stainless steel.

Kicker magnets: A kicker which recently failed showed signs of radiation damage to the potting rubber.

Main magnet insulation: No main magnets have failed in 30 years, but…

Installed radiation “dose tabs” around the ring in January shutdown to get a real estimate of dosage.

Conclusions

The Fermilab Booster has maintained a remarkable level of reliability over the last 30 years.

It has now reached unprecedented performance levels while maintaining reasonably strict beam loss standards.

We still have a lot to do to meet the demands of the future.


Every long and short section (2x24=48) has
	A horizontal and vertical BPM
		Can read out turn by turn for two or 50 time points for all 96
	A beam loss monitor
		Can snapshot all 96 for each cycle
	Horizontal and vertical trims
		Originally DC. Working on active control for the 24 high-b ones in each plane.
	Quads and Skew Quads
		Each has an individual DC setting plus common ramp.
Chromaticity sextupoles controlled by ramps
Some individual loss monitors at key locations.
Horizontal pinger for tune measurement
	Couples to V plane
	Doesn’t work at the moment (had to steal kicker)


	The proton source is very close the the specifications in the Run II Handbook.
	Although it’s the highest priority, support of collider operations is a relatively minor facet of life in the proton source.
	Proton source activities are dominated by the current and projected needs of the neutrino program (MiniBooNE+NuMI+??)
	Whatever a WBS chart may say, there’s not a separate proton source for RunII, MiniBooNE, NuMI, etc.


Total protons per batch: 4E12 with decent beam loss, 5E12 max.
Average rep rate of the machine:
	Injection bump magnets (7.5Hz)
	RF cavities (7.5Hz, maybe 15 w/cooling)
	Kickers (15 Hz)
	Extraction septa (was 2.5Hz, now 15Hz)
Beam loss
	Above ground:
		Shielding
		Occupancy class of Booster towers
	Tunnel losses
		Component damage
		Activiation of high maintenance items (particularly RF cavities)


Everything measured in 15 Hz “clicks”
Minimum Main Injector Ramp = 22 clicks = 1.4 s
MiniBoone batches “sneak in” while the MI is ramping.
Cycle times of interest
	Min. Stack cycle: 1 inj + 22 MI ramp = 23 clicks = 1.5 s
	Min. NuMI cycle: 6 inj + 22 MI ramp = 28 clicks = 1.9 s
	Full “Slipstack” cycle (total 11 batches):
		6 inject + 2 capture (6 -> 3) + 2 inject + 2 capture (2 -> 1) + 2 inject + 2 capture (2 -> 1) + 1 inject + 22 M.I. Ramp ---------------------- 39 clicks = 2.6 s


	The Time Line Generator (TLG) sequences all accelerator operations.
	Traditionally, each sequence (“module”) is independent, including any necessary Booster prepulses.
	This wasn’t really compatible with the goal of getting the maximum possible beam out of the Booster.
	In the new scheme:
		Standalone sequences are placed in the time line, with necessary prepulses
		MiniBooNE pulses are “trailer-hitched” to the end of these to achieve a specified average repetition rate, subject to an overall total rate.
		If there aren’t enough modules to trailer-hitch to, new modules will be built (still working the bugs out of this one).


	Running as we are now, the Booster can deliver a little over 1E20 protons per year – this is about a factor of six over typical stacking operations, and gives MiniBooNE about 20% of their baseline.
	NuMI will come on line in 2005, initially wanting about half of MiniBooNE’s rate, but hoping to increase their capacity – through Main Injector Improvements – until it is equal to MiniBooNE.
	Whatever the lab’s official policy, there will be great pressure (and good physics arguments) for running MiniBooNE and NuMI at the same time.
	-> By 2006 or so, the Proton Source might be called upon to deliver 10 times what it is delivering now.
	At the moment, there is no plan for assuring this, short of a complete replacement!
	So what are we going to try?…


	Shielding and new radiation assessment
	Vastly improved loss monitoring.
	New (MP02) extraction septum and power supply (enable high rep. rate running)
	New tuning strategies.


	Unshielded copper secondary collimators were installed in summer 2002, with a plan to shield them later.
	Due the the unexpected extent of the shielding and the difficulty of working in the area, the design was ultimately abandoned as unacceptable.
	Collimators were removed during the January shutdown.
	A new collimator system is being designed with steel secondary jaws fixed within a movable shielding body.
	Hope to have then ready before summer shutdown.


	The existing RF cavities form the primary aperture restriction (2 ¼” vs. 3 ¼”).










	They are high maintenance, so their activation is a worry.


	There is a plan for a new RF system with 5” cavities:
		Powered prototype built
		Building two vacuum prototypes for the summer shutdown with substantial machining done at universities.
		Evaluate these and procede (hopefully?) with full system.
	Total cost: $5.5M cavities + $5.5M power supplies (power supplies would pay for themselves in a few years)
	Is it worth it? On of the questions for the study group is how much improvement we might expect.


	The current injection bump dogleg (ORBUMP) magnets can ramp at 7.5 Hz, with a substantial temperature rise.
	Need to go to 10 to support MiniBooNE and NuMI.
	2 spares for the 4 (identical) magnets. Most likely failure mode probably repairable.
	Considering new design which will stretch existing magnets further apart, which will lower their current, but will require a pulsed injection septum between the first two.
	Can new design incorporate injection improvements??
	Some power supply issues as well:
		One full set of replacement SCR’s for the switch network.
		New switchbox being designed, but needs attention (or order more spare SCR’s).
		No spare for charge recovery choke.


	In order to Reduce radiation, a “notch” is made in the beam early in the booster cycle.
	Currently, the extraction time is based on the counted number of revolutions (RF buckets) of the Booster. This ensures that the notch is in the right place.
	The actual time can vary by > 5 usec!
	This is not a problem if booster sets the timing, but it’s incompatible with multi-batch running (e.g. Slipstacking or NuMI)
	We must be able to fix this total time so we can synchronize to the M.I. orbit.
	This is called “beam cogging”.


	Detect slippage of notch relative to nominal and adjust radius of beam to compensate.


	Historically, the booster has lacked a fundamental understanding of beam loss mechanisms.
	If (!!!) it is possible at all to go the the required beam flux, it will require some mitigation of beam loss.
	Recently, there has been an great increase in the involvement of the Beam Physics department in the Booster:
		Space charge group (W. Chou, et al) has begun to focus on the Booster again.
		Chuck Ankenbrandt has moved into Booster group as “Beam Physics Liaison” to help coordinate studies.
		Starting to make quantitative comparisons between predictions and measurement.
	An almost immediate result of this increased effort was the discovery of the “dogleg problem”….


	Took advantage of recent TeV Magnet failure to raise the Long 13 (dump) septum and turn off the associated dogleg.
	Doglegs almost exactly add, so this should reduce the effect by almost half.
	The mode of operation prevents short batching, booster study cycles and RDF operation.
	Had about 36 hours of study in this mode.
	Bottom Line: major improvement.


	Tune to minimize current?
		helped so far, but near limit.
		Maybe raise L13 septum a bit?
	Motorize L13 septum to switch modes quickly?
		Operational nightmare
	Eliminate L13?
		Find another way to short-batch
		Make a dump in MI-8 for Booster study cycles?
	Correctors?:
		These don’t look like quads, so can’t find a fix – yet.
	Spread out doglegs (effect goes down with square of separation):
		Not a lot of room. Maybe separate downstream magnets?
	Three-legged dog?
		Turn of the third of the four magnets.
		Need to increase first two reduces net improvement.


	Large Aperture Lattice Magnets?
		Obviously the “right” idea.
		Must match lattice AND (preferrably work with existing resonant circuit).
		Potential for big screw-up.
	Pulsed extraction bump?
		Straightforward magnet design.
		Only part of the lattice for a short period at the end of the cycle.
	New ideas welcome.


	GMPS (upgraded, OK)
	Transformers (serviced, OK)
	Vacuum system (being updated, finished 2003)
	Kicker PS charging cables
		Run three times over spec
		Evaluating improved design (better cable, LCW-filled heliac, etc)
	Low voltage power supplies, in particular Power 10 Series:
		Unreliable, some no longer serviced.
		Starting search for new supplier and evaluate system to minimize number of different types.
		Probably a few $100K to upgrade system.


	RF Hardware
		(original) Copper tuner cooling lines are beginning to spring leaks. Difficult to repair because they’re hot.
	High Level RF
		More or less original.
		Our highest maintenance item.
		Will probably last, BUT expensive to maintain.
		John Reid and Ralph Pasquinelli feel a new solid state system would pay for itself ($5.5M) in about four years.
	Low Level RF
		Many old modules, some without spares, some without drawings.
		An upgrade plan in place.
		Not expensive, but NEED people.
	Personnel!!!!


	Cables: frequent replacement of HV cables and connectors for ion pumps.
	Hoses: valve actuator hoses have failed and are now being replaced with stainless steel.
	Kicker magnets: A kicker which recently failed showed signs of radiation damage to the potting rubber.
	Main magnet insulation: No main magnets have failed in 30 years, but…
	Installed radiation “dose tabs” around the ring in January shutdown to get a real estimate of dosage.


	The Fermilab Booster has maintained a remarkable level of reliability over the last 30 years.
	It has now reached unprecedented performance levels while maintaining reasonably strict beam loss standards.
	We still have a lot to do to meet the demands of the future.