David Capista

The Fermilab Main Injector: high intensity operation and beam loss control

From 2005 through 2012, the Fermilab Main Injector provided intense beams of 120 GeV protons to produce neutrino beams and antiprotons. Hardware improvements in conjunction with improved diagnostics allowed the system to reach sustained operation at ~400 kW beam power. Transmission was very high except for beam lost at or near the 8 GeV injection energy where 95% beam transmission results in about 1.5 kW of beam loss. By minimizing and localizing loss, residual radiation levels fell while beam power was doubled. Lost beam was directed to either the collimation system or to the beam abort. Critical apertures were increased while improved instrumentation allowed optimal use of available apertures. We will summarize the improvements required to achieve high intensity, the impact of various loss control tools and the status and trends in residual radiation in the Main Injector.

Tune control in the Fermilab Main Injector

We describe methods used to measure and control tunes in the Fermilab Main Injector (FMI). Emphasis is given to software implementation of the operator interface, to the front-end embedded computer system, and handling of hysteresis of main dipole and quadrupole magnets. Techniques are developed to permit control of tune of the Main Injector through several acceleration cycles: from 8.9 GeV/c to 120 GeV/c, from 8.9 GeV/c to 150 GeV/c, and from 150 GeV/c to 8.9 GeV/c. Systems which automate the complex interactions between tune measurement and the variety of ramping options are described. Some results of tune measurements and their comparison with the design model are presented.

Operational aspects of the main injector large aperture quadrupole (WQB)

A two-year Large Aperture Quadrupole (WQB) Project was completed in the summer of 2006 at Fermilab. [1] Nine WQBs were designed, fabricated and bench-tested by the Technical Division. Seven of them were installed in the Main Injector and the other two for spares. They perform well. The aperture increase meets the design goal and the perturbation to the lattice is minimal. The machine acceptance in the injection and extraction regions is increased from 40pi to 60pi mm-mrad. This paper gives a brief report of the operation and performance of these magnets. Details can be found in Ref [2].

Collimation for the Fermilab booster to main injector transfer line

A collimation system has been created for removing proton beam halo in the 8 GeV transfer line from the Fermilab Booster to Main Injector. A pair of 1.14 meter long collimators with 5.08 cm rectangular apertures is installed in a 5-m straight section. Horizontal and vertical motion systems allow them to be positioned such that halo can be scraped from four sides. An additional pair of collimators, placed one cell (90 degrees) downstream, scrape halo which is of opposite phase. Each collimator pair can scrape about 600 Watts of beam power, limited by residual activation of beamline components and sump water outside of the beam line tunnel. Personnel exposure is reduced by surrounding the iron absorber with a layer of marble. Design features, radiation calculations and instrumentation considerations will be described.

Studies of beam properties and main injector loss control using collimators in teh Fermilab booster to main injector transfer line

High intensity operation of the Fermilab Main Injector has resulted in increased activation of machine components. Efforts to permit operation at high power include creation of collimation systems to localize losses away from locations which require maintenance. As a first step, a collimation system to remove halo from the incoming beam was installed in the Spring 2006 Facility Shutdown [1]. We report on commissioning studies and operational experience including observations of Booster beam properties, effects on Main Injector loss and activation, and operational results.

Fast beam stacking using RF barriers

Two barrier RF systems were fabricated, tested and installed in the Fermilab Main Injector. Each can provide 8 kV rectangular pulses (the RF barriers) at 90 kHz. When a stationary barrier is combined with a moving barrier, injected beams from the Booster can be continuously deflected, folded and stacked in the Main Injector, which leads to doubling of the beam intensity. This paper gives a report on the beam experiment using this novel technology.