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

Fermilab

Tevatron I Complex ( ) 3

Tevatron I Luminosity Parameters 4

TeV I Antiproton Source 5

Single batch stochastic cooling The Debuncher cools one batch of ~ 10 8 pbars at a time for 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. 6

Injection, Stacking and Cooling in the Accumulator 7

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. 8

Stack Tail Momentum Distribution with 4 x10 11 pbars 9

Evolution of the stack tail and core with time 10

Core Momentum Spread vs. Stack Size 11

Transverse Emittance vs. Stack Size 12

Extraction fraction vs. Stack Size 13

Run Statistics 14

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 15

Longitudinal Emittance vs. Booster Bunch intensity 16

Transverse Emittance vs. Booster Bunch Intensity 17

Run I Performance Statistics 18

Phase II Upgrade for Run II 19

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). 20

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. 21

Main Injector and Recycler 22

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 have been accumulated. The typical time between transfers is 1 hr. The accumulator stacking rate for these small stacks is x /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 and the accumulation rate does not decline with stash size. Typically stashes are mined when the stash is > 400 x 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%. 23

Stacking Rate vs. Stack Size during Run I 24

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. 25

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 N p is limited to < 30 x /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 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 /bunch. The peak L is between 2.8 to 3.2 x cm -2 s -1 when a full stash of 400 x is available. The record peak L is 3.47 x cm -2 s

Tevatron Performance for Run Ib and Goals for Run II 27

Peak Luminosity Run II 28

Run II Integrated Luminosity as of 8 Feb

Tevatron Complex in

Additional Slides 31

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 – 2 groups of h=3 bunches were used to produce 6 bunches/beam in 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. 32