Ultrafast Laser Laboratory
Muon targetry study: fast CCD camera capture of Mercury targets
In the last few years a renew interest in the idea of muon colliders arose because of the much advances in pion capture and cooling. It is now possible to raise the luminosity to the levels comparable to those of hadrons and electron machines. Interaction of a high energy GeV proton beam with a high-Z metal target results in maximal production of soft pions. Capturing these pions in a high magnetic field environment leads to efficient production of muons. Muons are just heavy electrons (200 times heavier than an electron), but their larger mass produce much less synchrotron radiation. Since muon decays into electrons and neutrinos, it also serves as a neutrino source. More information about muon colliders can be found here.
An issue for pion production in solid or liquid metal targets for muon collider sources and neutrino factories is the instantaneously deposited energy by the proton beam on the target. This energy will lead to rapid temperature rises, stress, and vaporization of the target. In the BNL-AGS-E951 experiment, the viability of the targetry and the capture of a 24 GeV proton pulse are studied. Details on the targetry studies can be found on the Muon Collider Targetry site at Princeton by Professor Kirk McDonald (spokesperson of the E951 experiment), and the Muon Collaboration site at BNL by Harold Kirk (spokesperson at BNL).
A targetry diagnostic tool using back illuminated laser shadow photography technique is used to image the events in high speed. A sequence of 16 laser pulses synchronized to the arrival of the proton beam is fired onto the target. The motion of the target after proton impact is frozen by using these very brief (150 ns) high intensity laser pulses. The image of the targetry is captured in this 150 ns duration by a SMD-64KIM fast CCD camera at the maximum rate of 1 million frames per second (1 microsecond per frame). The study provides benchmark values and allows the investigators to identify critical issues and limiting factors towards a muon collider.
Left: schematic of the mercury trough
target. Middle: experimental data using BNL SMD-64KIM fast CCD camera,
at 0.1 ms/frame, 0.15 microsecond exposure time pulsed by a laser beam
intensity of 8 Watt peak power. Right: experimental data using CERN Olympic
CCD camera, at 0.25 ms/frame, electronic shutter speed of 25 microsecond,
illumination is a 3 milliWatt CW red laser. The grid size on the image
is 1 cm. The energy of the proton is of 24 GeV in a duration 150 ns containing
3-4 TP (1 TP= 10^12 particles/pulse). Proton beam travels from left to
right 2 mm below the meniscus of the mercury trough. The maximum velocity
of mercury splash reaches ~75 m/s.
Left: schematic of mercury jet target. Middle: BNL experimental data, frame rate at 1 ms/frame, 0.15 microsecond exposure time pulsed by a laser beam intensity of 8 Watt peak power. Right: CERN experimental data, at 0, 0.75, 2, 7, and 18 ms frames. The electronic shutter speed is 25 microsecond and illumination is a 3 milliWatt CW red laser. The diameter
of the mercury jet is ~1 cm traveling to the right in a speed of ~2 m/s. The light illumination is in a diameter of ~10 cm. The maximum dispersal velocity of the mercury drops is ~ 10 m/s.
For more information or preprint request contact Thomas Y. F. Tsang
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Last Modified: Wednesday, 06-Feb-2013 22:33:56 EST