The Fermilab Accelerator Complex: Status and Challenges

Eric Prebys

FNAL Beams Division

Outline

Basic Accelerator Physics Concepts

Horizontal motion (lattice functions, emittance)

Tune plane

Longitudinal motion (phase stability, longitudinal emittance)

The Accelerator Complex

Proton Source (Preac, Linac, Booster)

Main Injector

Pbar source (target, debuncher, accumulator)

Tevatron

Recycler

Operational modes

The Challenges

Run II

MiniBooNE

NUMI

Tevatron

The Tevatron was the world’s first superconducting accelerator.

It accepts protons AND pbars at 150 GeV from the Main Injector. Typically:

36 proton bunches with 180E9 protons in each. (Run IIa goal: 270E9)

36 pbar bunches with 12E9 pbars in each. (Run IIa goal: 33E9)

These are accelerated to 980 GeV.

Collisions (“low beta”) are initiated at the B0 (CDF) and D0 detector regions.

These “stores” are kept for typically 16 hours, while more antiprotons are made for the next “shot”.

Recycler

The Recycler is an 8 GeV storage ring in the same tunnel as the Main Injector.

The main lattice elements (dipoles and quadrupoles) are made out of permanent magnets).

The Recycler can accept 8 GeV antiprotons from

The antiproton accumulator.

The Main Injector (after deceleration).

The Recycler can deliver these antiprotons to the Main Injector for acceleration.

The goal of the recycler is

To store antiprotons from the accumulator, thereby increasing the total antiproton production capacity.

To recover antiprotons from a Tevatron store for use in subsequent stores.

At the moment, the recycler is not being used in standard operation.

Primary Modes of Operation

Stacking: full booster batches (~5E12 p) are accelerated to 120 GeV by the Main Injector, and delivered to the pbar target about once every 3 seconds (limited by the rate at which they can be debunched and cooled. It takes 10-16 hours to get enough pbars for a “shot”.

Shot setup: various beamline tuning takes place. Most importantly, pbar transfer lines are tuned with reverse protons.

Proton Injection: about 7 53 MHz booster bunches are injected into the M.I., accelerated to 150 GeV and “coalesced” into a single bunch, which is injected into the Tevatron (x 36).

Antiproton Injection: part of the “core” of the accumulator is manipulated to a separate extraction orbit and about 11 53 MHz bunches are extracted to the M.I., where they are accelerated to 150 GeV, coalesced and injected into the tevatron at 150 GeV.

Acceleration/collision: The protons and pbars are accelerated together to 980 GeV over a few minutes. The beam is scraped, and the beta is reduced (“squeezed”) at the collision regions. Physics begins. During this time, the rest of the accelerator complex is totally free to do other things (primarily stacking).

MiniBooNE Operation: While the M.I. Is ramping, a chain of 8 GeV Booster batches is switched to the MiniBooNE beamline.

NUMI Operation: along with the stacking batch, 5 additional batches are loaded into the Main injector. These are accelerated along with the stacking batch and extracted to the NUMI line after it has been extracted.

How is Run II Going?

Why Haven’t Run IIa Goals been Met?

Number of pbars!!!

NOT (primarily) due to protons on target or pbar production rate.

Typically only around 50% of pbars from the accumulator make it to collisions.

Some of this is due to large emittances out of the accumulator. This gets worse with larger stacks.

Some is due to aperture and matching problems throughout the system.

Long range beam interactions in the Tevatron:

Limit total number of protons.

Due to aperture and helix problems.

General reliability problems:

It’s a very complicated system

If we lose the antiprotons, it takes at least 12 hours to recover.

The Plan

New cooling has been installed in the accumulator and is being tested. Initial results look good.

Studies continue to understand all the transfer efficiencies of the machines.

Continue to improve helix and aperture in Tevatron to reduce long range beam interaction.

Integrate recycler into accelerator operation some time in 2003.

(Near) Future Challenges

Two important neutrino experiments are coming on line soon:

MiniBooNE will use the 8GeV Booster beam and a detector 500 m away to look for neutrino oscillations in the range Dm²~1 eV² – the range indicated by the LSND experiment.

NUMI will use the 120 GeV Main Injector beam and a detector 750 km away to look for neutrino oscillations in the range of Dm²~10^-5 eV² – the range indicated by atmospheric and solar neutrino data.

Both of these experiments place a major challenge on the Booster – arguably the only more or less original part of the Fermilab accelerator complex.

What’s so Hard About Neutrino Physics (from the Accelerator Standpoint)?

Probability that a proton on the AP target will produce an accumulated pbar:
.000015 (1.5E-5)

Probability that a proton on the MiniBooNE target will result in a detected neutrino:
.000000000000004 (4E-15)

Probability that a proton on the NUMI target will result in a detected neutrino at the MINOS far detector:
.000000000000000025 (2.5E-17)

Þ Need more protons in a year than Fermilab has produced in its lifetime!!

What Limits Total Proton Intensity?

Maximum number of Protons the Booster can stably accelerate: 5E12

Maximum average Booster rep. Rate: currently 2.5 Hz, soon 7.5 Hz

(NUMI only) Maximum number of booster batches the Main Injector can hold: currently 6, possibly go to 11

(NUMI only) Minimum Main Injector ramp cycle time (NUMI only): 1.4s+loading time

Losses in the Booster:

Above ground radiation

Damage and/or activation of tunnel components

Proton Timelines

Everything measured in 15 Hz “clicks”

Minimum M.I. Ramp = 22 clicks = 1.4 s

MiniBoone batches “don’t count”.

Cycle times of interest

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

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

Booster Repetition Rate Limits

Presently, the Booster is limited to an average rep. Rate of 2.5 Hz, which would only yield a small fraction of the desired MiniBooNE intensity. The primary limitation is the pulsed extraction septum magnet (MP02).

A new power supply will go in in the next few weeks, which will raise this rate to 4.5 Hz, which would give about half the nominal MiniBooNE rate.

A new magnet will go in during the January shutdown which will allow the Booster to go to 7.5 Hz – enough for MiniBooNE or NUMI.

In order to run both MiniBooNE and NUMI, we need

More cables for the extraction septum.

Cooling for the RF cavities (or new RF cavities)

A new “bump” magnet, which steers beam out during injection.

Above Ground Radiation

Main worry are the high occupancy areas in the Booster towers.

Shielding has been added both in the tunnel and to the first floor of the Booster towers.

Offices have been moved to reclassify some worrisome areas.

Best Performance + Shielding + BooNE Intensities

Booster Tunnel Losses

Harder to quantify – no hard limits

Major worry is activation of high maintenance components (e.g. RF cavities).

Administrative limit set at twice the total power loss during “messy” stacking (for 9 times the beam!!!).

If we had to run tomorrow, we could deliver roughly 20% of the nominal MiniBooNE intensity under this scenario.

Steps are being taken to reduce beam losses and proton source consistency.

Collimators

Other Improvements

Beam control: programmable trim magnet control cards now allow control of the orbit throughout the cycle.

Improved beam monitoring: a number of new beam diagnostics, including a real time tune measurement, had been or are being commissioned.

New monitoring and analysis tools: we have been pledged support from computing division, which we plan to use to develop improved tools for monitoring and analyzing the performance of the proton source.

Summary

The Fermilab accelerator complex is very complex and versatile.

It presents many challenges which keep us busy now and in the foreseeable future.

We’re always looking for people to help out.


	Basic Accelerator Physics Concepts
		Horizontal motion (lattice functions, emittance)
		Tune plane
		Longitudinal motion (phase stability, longitudinal emittance)
	The Accelerator Complex
		Proton Source (Preac, Linac, Booster)
		Main Injector
		Pbar source (target, debuncher, accumulator)
		Tevatron
		Recycler
		Operational modes
	The Challenges
		Run II
		MiniBooNE
		NUMI


	The Tevatron was the world’s first superconducting accelerator.
	It accepts protons AND pbars at 150 GeV from the Main Injector. Typically:
		36 proton bunches with 180E9 protons in each. (Run IIa goal: 270E9)
		36 pbar bunches with 12E9 pbars in each. (Run IIa goal: 33E9)
	These are accelerated to 980 GeV.
	Collisions (“low beta”) are initiated at the B0 (CDF) and D0 detector regions.
	These “stores” are kept for typically 16 hours, while more antiprotons are made for the next “shot”.


	The Recycler is an 8 GeV storage ring in the same tunnel as the Main Injector.
	The main lattice elements (dipoles and quadrupoles) are made out of permanent magnets).
	The Recycler can accept 8 GeV antiprotons from
		The antiproton accumulator.
		The Main Injector (after deceleration).
	The Recycler can deliver these antiprotons to the Main Injector for acceleration.
	The goal of the recycler is
		To store antiprotons from the accumulator, thereby increasing the total antiproton production capacity.
		To recover antiprotons from a Tevatron store for use in subsequent stores.
	At the moment, the recycler is not being used in standard operation.


	Stacking: full booster batches (~5E12 p) are accelerated to 120 GeV by the Main Injector, and delivered to the pbar target about once every 3 seconds (limited by the rate at which they can be debunched and cooled. It takes 10-16 hours to get enough pbars for a “shot”.
	Shot setup: various beamline tuning takes place. Most importantly, pbar transfer lines are tuned with reverse protons.
	Proton Injection: about 7 53 MHz booster bunches are injected into the M.I., accelerated to 150 GeV and “coalesced” into a single bunch, which is injected into the Tevatron (x 36).
	Antiproton Injection: part of the “core” of the accumulator is manipulated to a separate extraction orbit and about 11 53 MHz bunches are extracted to the M.I., where they are accelerated to 150 GeV, coalesced and injected into the tevatron at 150 GeV.
	Acceleration/collision: The protons and pbars are accelerated together to 980 GeV over a few minutes. The beam is scraped, and the beta is reduced (“squeezed”) at the collision regions. Physics begins. During this time, the rest of the accelerator complex is totally free to do other things (primarily stacking).
	MiniBooNE Operation: While the M.I. Is ramping, a chain of 8 GeV Booster batches is switched to the MiniBooNE beamline.
	NUMI Operation: along with the stacking batch, 5 additional batches are loaded into the Main injector. These are accelerated along with the stacking batch and extracted to the NUMI line after it has been extracted.


	Number of pbars!!!
		NOT (primarily) due to protons on target or pbar production rate.
		Typically only around 50% of pbars from the accumulator make it to collisions.
		Some of this is due to large emittances out of the accumulator. This gets worse with larger stacks.
		Some is due to aperture and matching problems throughout the system.
	Long range beam interactions in the Tevatron:
		Limit total number of protons.
		Due to aperture and helix problems.
	General reliability problems:
		It’s a very complicated system
		If we lose the antiprotons, it takes at least 12 hours to recover.


	New cooling has been installed in the accumulator and is being tested. Initial results look good.
	Studies continue to understand all the transfer efficiencies of the machines.
	Continue to improve helix and aperture in Tevatron to reduce long range beam interaction.
	Integrate recycler into accelerator operation some time in 2003.


	Two important neutrino experiments are coming on line soon:
		MiniBooNE will use the 8GeV Booster beam and a detector 500 m away to look for neutrino oscillations in the range Dm²~1 eV² – the range indicated by the LSND experiment.
		NUMI will use the 120 GeV Main Injector beam and a detector 750 km away to look for neutrino oscillations in the range of Dm²~10^-5 eV² – the range indicated by atmospheric and solar neutrino data.
	Both of these experiments place a major challenge on the Booster – arguably the only more or less original part of the Fermilab accelerator complex.


	Probability that a proton on the AP target will produce an accumulated pbar: .000015 (1.5E-5)
	Probability that a proton on the MiniBooNE target will result in a detected neutrino: .000000000000004 (4E-15)
	Probability that a proton on the NUMI target will result in a detected neutrino at the MINOS far detector: .000000000000000025 (2.5E-17)

	Þ Need more protons in a year than Fermilab has produced in its lifetime!!


	Maximum number of Protons the Booster can stably accelerate: 5E12
	Maximum average Booster rep. Rate: currently 2.5 Hz, soon 7.5 Hz
	(NUMI only) Maximum number of booster batches the Main Injector can hold: currently 6, possibly go to 11
	(NUMI only) Minimum Main Injector ramp cycle time (NUMI only): 1.4s+loading time
	Losses in the Booster:
		Above ground radiation
		Damage and/or activation of tunnel components


Everything measured in 15 Hz “clicks”
Minimum M.I. Ramp = 22 clicks = 1.4 s
MiniBoone batches “don’t count”.
Cycle times of interest
	Stack cycle: 1 inj + 22 MI ramp = 23 clicks = 1.5 s
	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


	Presently, the Booster is limited to an average rep. Rate of 2.5 Hz, which would only yield a small fraction of the desired MiniBooNE intensity. The primary limitation is the pulsed extraction septum magnet (MP02).
	A new power supply will go in in the next few weeks, which will raise this rate to 4.5 Hz, which would give about half the nominal MiniBooNE rate.
	A new magnet will go in during the January shutdown which will allow the Booster to go to 7.5 Hz – enough for MiniBooNE or NUMI.
	In order to run both MiniBooNE and NUMI, we need
		More cables for the extraction septum.
		Cooling for the RF cavities (or new RF cavities)
		A new “bump” magnet, which steers beam out during injection.


	Main worry are the high occupancy areas in the Booster towers.
	Shielding has been added both in the tunnel and to the first floor of the Booster towers.
	Offices have been moved to reclassify some worrisome areas.


	Harder to quantify – no hard limits
	Major worry is activation of high maintenance components (e.g. RF cavities).
	Administrative limit set at twice the total power loss during “messy” stacking (for 9 times the beam!!!).
	If we had to run tomorrow, we could deliver roughly 20% of the nominal MiniBooNE intensity under this scenario.
	Steps are being taken to reduce beam losses and proton source consistency.


	Beam control: programmable trim magnet control cards now allow control of the orbit throughout the cycle.
	Improved beam monitoring: a number of new beam diagnostics, including a real time tune measurement, had been or are being commissioned.
	New monitoring and analysis tools: we have been pledged support from computing division, which we plan to use to develop improved tools for monitoring and analyzing the performance of the proton source.


	The Fermilab accelerator complex is very complex and versatile.
	It presents many challenges which keep us busy now and in the foreseeable future.
	We’re always looking for people to help out.