Antiproton, positron, and electron imaging with a microchannel plate/phosphor detector

Andresen, Gorm Bruun; Bertsche, W.; Bowe, P. D.; Bray, C. C.; Butler, E.; Cesar, C. L.; Chapman, S.; Charlton, M.; Nasr, S. Seif El; Fajans, J.; Fujiwara, M.; Gill, D. R.; Hangst, J. S.; Hardy, W. N.; Hayano, R.; Hayden, M. E.; Humphries, A. J.; Hydomako, R.; Jørgensen, L. V.; Kerrigan, Sean; Kurchaninov, L. L.; Lambo, R.; Madsen, N.; Nolan, P.; Olchanski, K.; Olin, Å.; Povilus, A.; Pusa, P.; Sarid, E.; Silveira, D. M.; Storey, J. W.; Thompson, R. I.; Werf, D. P. van der; Yamazaki, Y.; Collaboration, ALPHA

doi:10.1063/1.3266967

Cited by 39 publications

(25 citation statements)

References 11 publications

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“…Measurements of the transverse density profile were made by ejecting the particles onto an MCP/phosphor/CCD imaging device [13]. It was seen that, as evaporation progressed, the cloud radius increased dramatically-see Fig.…”

Section: Evaporative Coolingmentioning

confidence: 99%

Towards antihydrogen trapping and spectroscopy at ALPHA

et al. 2011

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Spectroscopy of antihydrogen has the potential to yield high-precision tests of the CPT theorem and shed light on the matter-antimatter imbalance in the Universe. The ALPHA antihydrogen trap at CERN's Antiproton Decelerator aims to E. Butler et al. prepare a sample of antihydrogen atoms confined in an octupole-based Ioffe trap and to measure the frequency of several atomic transitions. We describe our techniques to directly measure the antiproton temperature and a new technique to cool them to below 10 K. We also show how our unique position-sensitive annihilation detector provides us with a highly sensitive method of identifying antiproton annihilations and effectively rejecting the cosmic-ray background.

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Section: Evaporative Coolingmentioning

confidence: 99%

Towards antihydrogen trapping and spectroscopy at ALPHA

et al. 2011

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“…Electron multiplier microchannel plates (MCPs) offer a variable amplification and their applicability to antiproton monitoring has already been demonstrated [17]. Approximately 10 5 antiprotons delivered in about 10 ms can be observed by an MCP placed directly in the beam path.…”

Section: A Motivationmentioning

confidence: 99%

Beam diagnostics for low energy beams

Harasimowicz

Welsch

Coséntino³

et al. 2012

Phys. Rev. ST Accel. Beams

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Low-energetic ion and antimatter beams are very attractive for a number of fundamental studies. The diagnostics of such beams, however, is a challenge due to low currents down to only a few thousands of particles per second and significant fraction of energy loss in matter at keV beam energies. A modular set of particle detectors has been developed to suit the particular beam diagnostic needs of the ultralowenergy storage ring (USR) at the future facility for low-energy antiproton and ion research, accommodating very low beam intensities at energies down to 20 keV. The detectors include beam-profile monitors based on scintillating screens and secondary electron emission, sensitive Faraday cups for absolute intensity measurements, and capacitive pickups for beam position monitoring. In this paper, the design of all detectors is presented in detail and results from beam measurements are shown. The resolution limits of all detectors are described and options for further improvement summarized. Whilst initially developed for the USR, the instrumentation described in this paper is also well suited for use in other low-intensity, low-energy accelerators, storage rings, and beam lines.

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“…Further, the magnetic system is astigmatic forp 's, and the resulting images are always elliptical. The response of the imaging system top 's is more than 100× greater than it is for e − 's because thē p annihilations greatly enhance the response [8], so the relative brightness of the e − andp images can be deceiving. For instance, in Fig.…”

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confidence: 99%

“…Images like those shown in Fig. 1 are obtained destructively [8]. One of the electrostatic well walls that confine the mixed plasmas is lowered, thereby allowing the plasmas to flow out of the uniform solenoidal region (1 T or 3 T) and onto a micro-channel plate (MCP)/phosphor screen/CCD imaging system, yielding an axially-integrated image of the plasma densities.…”

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confidence: 99%

Centrifugal Separation and Equilibration Dynamics in an Electron-Antiproton Plasma

Andresen

Ashkezari²,

Baquero-Ruiz³

et al. 2011

Phys. Rev. Lett.

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Charges in cold, multiple-species, non-neutral plasmas separate radially by mass, forming centrifugally-separated states. Here, we report the first detailed measurements of such states in an electron-antiproton plasma, and the first observations of the separation dynamics in any centrifugally-separated system. While the observed equilibrium states are expected and in agreement with theory, the equilibration time is approximately constant over a wide range of parameters, a surprising and as yet unexplained result. Electron-antiproton plasmas play a crucial role in antihydrogen trapping experiments. This paper presents the first images and detailed measurements of centrifugal separation in an electron (e − )-antiproton (p) plasma system. Figure 1 shows images of two such centrifugally-separated plasmas in the ALPHA antihydrogen trapping apparatus [6]. (Recently, the ATRAP collaboration reported [7] indirect observations of centrifugally-separated states in a e − -p system.) We also report the first measurements of the separation dynamics in any centrifugally-separated system. Specifically, we report the timescale on which thep distribution comes into equilibrium in response to changes in the e − temperature and density. Depending on the type of change in the e − parameters, thep equilibration time scale varies from milliseconds to seconds, but it is notable that the time scale is approximately seventy milliseconds for a wide range of changes. Not all of these time scales can be explained by previously explored theoretical mechanisms.Thep 's will separate from the e − 's when the E × B rotational velocity rω R at the plasma edge starts to exceed the thermal velocity of thep 's. In the limit, common in this paper, that there are fewp 's compared to e − 's, thep radial density will be given by np(r, z) ∼ n e − (r, z) exp [(r/Lp) 2 ], where n e − (r, z) is the e − radial density, and thep edge scale length Lp is where T is the plasma temperature, mp is thep mass, n e − = n e − (0, 0) is the central e − density, and e is the unit charge. The rightmost expression holds only in the long plasma limit.

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Antiproton, positron, and electron imaging with a microchannel plate/phosphor detector

Cited by 39 publications

References 11 publications

Towards antihydrogen trapping and spectroscopy at ALPHA

Towards antihydrogen trapping and spectroscopy at ALPHA

Beam diagnostics for low energy beams

Centrifugal Separation and Equilibration Dynamics in an Electron-Antiproton Plasma

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