Robert R. Wilson Prize Talk John Peoples

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Robert R. Wilson Prize Talk John Peoples April APS Meeting: February 14, 2010 1

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Robert R. Wilson Prize Talk John Peoples. April APS Meeting: February 14, 2010. Fermilab 1982. Tevatron I Complex (1987-1989). Tevatron I Luminosity Parameters. Luminosity L= (f 0 BN pbar N p Fγ)/(2β* (ε v + ε h )) Tevatron Collider Parameters - PowerPoint PPT Presentation

Transcript of Robert R. Wilson Prize Talk John Peoples

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Robert R. Wilson Prize TalkJohn Peoples

April APS Meeting: February 14, 2010

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Fermilab 1982

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Tevatron I Complex (1987-1989)

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Tevatron I Luminosity Parameters

Luminosity

L= (f0 BNpbar Np Fγ)/(2β* (εv + εh ))

Tevatron Collider Parameters Luminosity Goal: L= 10 30 cm -2 s -1

Energy: E= 900 GeV β * = 100 cmε v , ε h = 24 mm-mr N p , N pbar = 6 x 10 10

Number of Bunches/beam: B = 3Luminosity Lifetime: T = L(dL/dt) -1 ~ 12 hr

TL

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TeV I Antiproton Source

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Single batch stochastic cooling

• The Debuncher cools one batch of ~ 10 8 pbars at a time for 2 - 3 s (one Main Ring cycle) and then transfers the batch to the Accumulator.

• The cooling time is proportional to the number of particles (N), the mixing (M), the noise to signal ration (U) and inversely proportional to the bandwidth (W)T = ε (dε/dt) -1 α N(M+U)/W

• Typical initial cooling times are about 0.5 s .

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Injection, Stacking and Cooling in the Accumulator

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Stack tail cooling system

• The stack tail pickups are placed in a region of high dispersion (9 m). A displacement of 10 mm radially inward corresponds to an energy decrease of 10 MeV.

• The gain of the stack tail pickups decreases exponentially with the radial distance from the pickups, which is proportional to energy.

• The beam is cooled slowly where dN/dE is large and quickly where dN/dE is small. An exponential increase in dN/dE will provide a constant flux of pbars into the core momentum cooling system.

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Stack Tail Momentum Distribution with 4 x10

11 pbars

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Evolution of the stack tail and core with time

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Core Momentum Spread vs. Stack Size

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Transverse Emittance vs. Stack Size

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Extraction fraction vs. Stack Size

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1988-89 Run Statistics

Design Goal Achieved 1988-89

Number of bunches/beam 3 6

Number of p’s/bunch 6 x 1010 5.5 x 1010

Number of ’s/bunch 6 x 1010 2.5 x 1010

Β* at BØ [cm] 100 cm 55 cm

Єv, ЄH protons [mm-mr] 24 24

Єv, ЄH antiprotons [mm-mr] 24 18

Energy [GeV] 900 900

Peak Luminosity [cm-2 sec-1] 1030 2 x 1030

Initial Luminosity Lifetime [hr] 12 12

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Phase I Upgrade of the Fermilab Accelerator Complex

The elements of the phase I upgrade for run I were:• Matched low beta insertions for CDF (B0) and D0• System of electrostatic separators to reduce the

number of beam-crossings to two (CDF and D0)• Linac energy upgrade from 200 MeV to 400 MeV• Improvements to the pbar target station and cooling

systems• Improvements to the controls and beam position

monitors systems

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Longitudinal Emittance vs. Booster Bunch intensity

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Transverse Emittance vs. Booster Bunch Intensity

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Run I Performance Statistics

Run Ia Run Ib

Duration August 1992-June 1993 November 1993-February 1996

Peak Luminosity 9.2 x 1030 cm-2 sec-1 2.5 x 1030 cm-2 sec-1

Typical Luminosity 5 x 1030 cm-2 sec-1 1.6 x 1030 cm-2 sec-1

Stacking Rate 4.85 x 1010 hr-1 7.02 x 1010 hr-1

Maximum Stack Size 150 x1010 221 x 1010

Delivered Integrated Luminosity 31.7 pbs-1 147 pbs-1

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Phase II Upgrade for Run II

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Elements of the Phase II Upgrade

• Main Injector replaces the Main Ring and does all of its functions much better

• Recycler provides a third and substantially better cooling system with electron and stochastic cooling.

• A set of injection kickers to enable 36 bunch operation• Bandwidths of all pbar source cooling systems doubled• Significant improvements to the controls and beam

position monitor systems to make transfers faster and more efficient (especially pbars).

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Main Injector

• Main Injector is 150/120 GeV proton synchrotron with a circumference of 3.3 km.

• Its functions for colliding beams are:– Accepts 8 GeV protons from the Booster, accelerates them to

120 GeV and delivers them to the Pbar target station for pbar production and subsequent collection in the pbar source.

– Accepts short bunch trains of 8 GeV pbars from the Recycler and 8 GeV protons from the Booster, accelerates them to 150 GeV, coalesces them in to 4 bunches for pbars and 2 bunches for protons and then transfers them to the Tevatron.

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Main Injector and Recycler

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Recycler• The Recycler is an 8 GeV storage ring for pbars. It is made mainly of

permanent alternating gradient magnets. Pbars are transferred from the Accumulator after stacks of 25 x 10 10 have been accumulated. The typical time between transfers is 1 hr.

• The accumulator stacking rate for these small stacks is 25- 30 x 10 10 /hr.

• The pbars are cooled and stashed by a few x 100 mA cold relativistic electron beam (4.3 MeV). The stash size can be up to 500 x 10 10 and the accumulation rate does not decline with stash size. Typically stashes are mined when the stash is > 400 x 10 10 .

• The formation of dense bunches in the Main Injector at 150 GeV and subsequent coalescing is very efficient. Typically the transfer efficiency from Recycler to the Tevatron at low β is > 80%.

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Stacking Rate vs. Stack Sizeduring Run I

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Selection of the number of Bunches, B• L is proportional to B• The bunch spacing is determined by the

selected sub-harmonic of the Tevatron 53 MHz RF system (h=3 x7 x53 = 1113). – h=53 provides a bunch spacing of 396 ns. It is

being used in Run II to produce 3 groups of 12 bunches with 400 ns spacing for each beam.

– The separation of the groups, about 2 µ s, is used for aborts, injection and cogging.

– 36 bunches/beam is standard in Run II.

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Collider Operation with the Main Injector and Recycler

• Each beam has 36 bunches and circulates on helical orbits separated by > 5 sigma except at B0 (CDF) and D0 where the beams collide

• Np is limited to < 30 x 10 10 /bunch in order to keep the pbar beam-beam tune shift to < .025. When this is exceeded the initial luminosity lifetime decreases < 6 hr quickly

• 2.7 x 10 11 protons/bunch are consistently delivered to low β with a bunch coalescing efficiency of 70%. The luminosity lifetime is typically 6 hr.

• N pbar is generally in the range of 7 to 9 x 10 10 /bunch.• The peak L is between 2.8 to 3.2 x 10 32 cm -2 s -1 when a full

stash of 400 x 10 10 is available. • The record peak L is 3.47 x 10 32 cm -2 s -1 .

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Tevatron Performance for Run Ib and Goals for Run II

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Peak LuminosityRun II

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Run II Integrated Luminosity as of 8 Feb 2010

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Tevatron Complex in 2010

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Additional Slides

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Selection of the number of Bunches, B• L is proportional to B• The bunch spacing is determined by the selected sub-

harmonic of the Tevatron 53 MHz RF system (h=3 x7 x53 = 1113). – h=3 is the minimum value to provide collisions at B0 (CDF)

and D0. h=3 was used in 1987.– 2 groups of h=3 bunches were used to produce 6

bunches/beam in 1988-89 and Run I. – h=53 provides a bunch spacing of 400 ns. It was used Run

II to produce 3 groups of 12 bunches with 400 ns spacing for each beam. The separation of groups is about 2 µ s. 36 bunches/beam is standard in Run II.