Ioanis Kourbanis

Multi-batch slip stacking in the main injector at fermilab

The Main Injector (MI) at Fermilab is planning to use multi-batch slip stacking scheme in order to increase the proton intensity at the NuMI target by about a factor of 1.5.[1] [2] By using multi-batch slip stacking, a total of 11 Booster batches are merged into 6, 5 double ones and one single. We have successfully demonstrated the multi- batch slip stacking in MI and accelerated a record intensity of 4.6E13 particle per cycle to 120 GeV. The technical issues and beam loss mechanisms for multi- batch slip stacking scheme are discussed.

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.

Collimation system design for beam loss localization with slipstacking injection in the Fermilab main injector

Results of modeling with the 3-D STRUCT and MARS 15 codes of beam loss localization and related radiation effects are presented for the slipstacking injection to the Fermilab Main Injector. Simulations of proton beam loss are done using multi-turn tracking with realistic accelerator apertures, nonlinear fields in the accelerator magnets and time function of the RF manipulations to explain the results of beam loss measurements. The collimation system consists of one primary and four secondary collimators. It intercepts a beam power of 1.6 kW at a scraping rate of 5% of 5.5E+13 ppp, with a beam loss rate in the ring outside the collimation region of 1 W/m or less. Based on thorough energy deposition and radiation modeling, a corresponding collimator design was developed that satisfies all the radiation and engineering constraints.

A wide aperture quadrupole for the Fermilab main injector synchrotron

During the design of the Fermilab Main Injector synchrotron it was recognized that the aperture was limited at the beam transfer and extraction points by the combination of the Lambertson magnets and the reused Main Ring quadrupoles located between the Lambertsons. Increased intensity demands on the Main Injector from antiproton production for the collider program, slow spill to the meson fixed target program, and high intensity beam to the high energy neutrino program have led us to replace the aperture-limiting quadrupoles with newly built magnets that have the same physical length but a larger aperture. The magnets run on the main quadrupole bus, and must therefore have the same excitation profile as the magnets they replaced. We present here the design of the magnets, their magnetic performance, and the accelerator performance.

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.

Present and future high-energy accelerators for neutrino experiments

There is an active neutrino program making use of the high-energy (larger than 50 GeV) accelerators both in USA at Fermilab with NuMI and at CERN in Europe with CNGS. In this paper we will review the prospects for high intensity high energy beams in those two locations during the next decade.

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.

Controlling the resistive wall instability in the Fermilab Main Ring

The Fermilab Main Ring has a strong transverse instability identified as a resistive wall. Previous methods of dealing with this problem have primarily been to find settings of tune, chromaticity, and octupole that result in stable operation. Controlling this instability in this manner has had limited success and reduces beam lifetime. A new damper system has been installed in the Main Ring to control this instability. This damper effectively provides a negative impedance to the accelerator to cancel the effects of the resistive wall. With this damper in operation we have been able to adjust the tune, chromaticity, and octupole settings to improve beam efficiency without becoming unstable due to the resistive wall of the accelerator.