Beam physics of the 8-GeV H-minus linac Page: 2 of 18
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differences and general understanding of neutrino properties are goals of the
U.S. neutrino program the accelerator is designed to address. There are
many other possible applications such as fixed target programs or acceler-
ation of other species (e-, p, p, etc...) as discussed in References [2] and
[3]. This paper presents the beam dynamics of the FNAL Proton Driver
performed with the simulation codes TRACK [4] and ASTRA [5]. Developed by
Argonne National Laboratory to fulfill the requirement of heavy-ion linacs,
TRACK is the primary tool in the design of the accelerator. ASTRA, developed
by the Deutsches Elektronen-Synchrotron laboratory (Hamburg, Germany),
is mainly used for the design of electron photoinjectors and we present for
the first time the application of this code for hydrogen ion linacs.
2. Layout of the linac
The FNAL Proton Driver is designed to deliver 1.56-1014 protons to the
Main Injector in typical pulse lengths of 1 msec leading to an average beam
current of 25 mA per pulse [6]. At a kinetic energy of 8 GeV and a repetition
rate of 10 Hz the corresponding beam average power is -2 MW.
A schematic layout of the FNAL Proton Driver is shown in Figure 1.
The H- beam from the Ion Source is bunched and accelerated to 2.5 MeV
by a Radio-Frequency Quadrupole (RFQ, [7]) operating at 325 MHz. At
that energy, a Medium Energy Beam Transport (MEBT) system provides
the space for a fast chopper that eliminates the unwanted bunches and forms
an optimal beam time structure for multi-turn charge-exchange injection into
the Main Injector with minimum uncontrolled beam losses. This chopping
decreases the beam average current over the 1 msec pulse from -45 mA to
-25 mA. Acceleration from 2.5 MeV to 10 MeV is provided by 16 room
temperature cross-bar H-type (CH) cavities. Above 10 MeV, SC RF struc-
tures are used. Two types of Single Spoke Resonators and one type of Triple
Spoke Resonators (SSR1, SSR2, TSR) accelerate the beam up to -420 MeV.
At this energy spoke cavities become less efficient and the beam is further
accelerated up to 8 GeV using Squeezed ILC (S-ILC, 7G = 0.81) and ILC
(OG = 1.0) 1.3 GHz cavities. An outstanding feature of the linac is the use of
high power ferrite vector modulators [8] that allows the fan-out of RF power
from a klystron to feed multiple cavities.
Superconducting solenoids have been selected as the focusing elements for
the front-end between the RFQ and TSR sections. As discussed in [9], several
advantages arise from the use of SC solenoids compared to the standard2
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Carneiro, J.-P.; /Fermilab; Mustapha, B.; Ostroumov, P.N. & /Argonne. Beam physics of the 8-GeV H-minus linac, article, November 1, 2008; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc930235/m1/2/: accessed April 26, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.