The beamline for the second axis of the Dual Axis Radiographic Hydrodynamic Test Facility

Abstract

During normal DARHT II I operation , the beam exiting the accelerator will he wcll characterized by its nominal de sign parameters of 20-MeV, 2000-Amperes, 2-psee pulse length , and 3 em-1m llllnornlaiized emitlance. Normal operation will have the heam delivered to a hcam dump via several DC magnets. A 2-way kicker magnet is used to deflect portions of the beam into the straight ahead beHmline leading to either a diagnostic heamline or to the converter target beamline. During start up and or beam development periods , the he am exiling the accelerator may have parameters outside the acceptable range of values for normal operation. The Enge beam line must accommodate this range of unacceptablc beam parameters, delivering the entire 80 Kilojoule of heam to the dump even though the energy, emittance, and/or match is outside the nominal design range. THE UEAMLINEThe beamline system co nsi sts of four operationally distinct beam lines: I) the Bilge beamline, 2) the main dump beamline, 3) the diagnostic heal11linc, ami 4) the target beamline. These lines share some components and floor space within the DARHT huilding. The heamline considered here extends from the exit of the accelcrator , SOlllC 12 metcrs beforc the beginning of the shielding wall. Depending on the magnet settings, the heam from the accelerator is transported to the "Enge clump," a "tuning dump," kicked into a "diagnostic line," or kicked into the "transport line" with eventual delivery to the x ray converter target outside the shiel ding wall. The two dump beamlines and diagnostic bcamline arc constrained to lie within thc DARHT shielding wall. The be amlin e to the converter target penetrates the shielding wall and extends some 5.9 meters from the exit of that wall to the converter target. When ready to produce a radiograph we usc the 2�way kicker Lo cancel the DC rield or the kicker bias dipole allowing a scction of the beam to pass undefleeted into the target beamline. We repeat this up to four times during the 2-�lsec-beaTll duration, producing up -----------_. to four beam pulses separated by 600 ns. The x-rays are produced when the electrons arc tightl y focused by the final focusing lens to the earrect position on a Bremsstrahlung target. 2.TH]�REAMThe beam delivered hy the DARI-IT accelerator consists of a 2-�lsec-beal11 body of 20-McV electrons, This is preceded by the "heam head ," a O.4-Jlscc dribble of electrons X-20 MeV with current i ncreasing from .1 ta 2 kA. If a beam head cleanup section is used <lner the first 8 cells, this head is reduced to a O.05-Jlsec dribble of particles in the energy range 0]" 15�20 MeV, current 0 to 2 kA 3. THE ENGE REAMLINE The Enge heaml ine must he capahle of handling the entire lIO Kilojoule af thermal energy over a wide range of beam energy, emitta nc e , or other parameLers. This heamline is capable of handling and characterizing the beam from the accelerator "no maLleI''' what its cnergy, emi [(ance, or other parameters arc. This beam line consists of a series of solenoid lens leadi ng to all Enge magne...

Particle Beam Radiography

“…After exiting the LIA, the long pulse is sliced into four shorter pulses by a fast kicker system in the downstream transport (DST), with the un-kicked beam diverted to an offline dump [122][123][124][125][126][127][128][129][130]. The durations of the kicked pulses are individually programmable, from 20 ns to >100 ns, and this feature is used to tune the individual doses to the dynamic experiment.…”

Transverse centroid oscillations in solenoidially focused beam transport lattices

“…Solenoidal focusing is employed in a variety of ion and electron beam transport applications such as ion beam driven experiments in warm dense matter [1], intense electron beams for driving flash x-ray radiography [2], and electron cooling for hadron beams [3,4]. Such applications typically require precise control of the beam centroid to: control the placement of the beam spot on target, maintain alignment of the beam with the field in cooling applications, and control a variety of deleterious processes that are enhanced with increasing amplitude of centroid oscillations in the machine.…”

The DARHT-II downstream transport beamline

“…Beam transport studies for this design have been performed [2]. Figure 1 shows the layout for the downstream elements.…”

“…The proposed system using a quadrupole magnet [2] allows for a larger beam pipe radius than the more conventional septum dipole magnet studied earlier. This increases the energy acceptance of the transport line to the main beam dump.…”