The OLYMPUS internal hydrogen target

Bernauer, J. C.; Carassiti, V.; Ciullo, G.; Henderson, Brian S.; Ihloff, E.; Kelsey, J.; Lenisa, P.; Milner, R.; Schmidt, Axel; Statera, M.

doi:10.1016/j.nima.2014.04.029

Cited by 21 publications

(31 citation statements)

References 6 publications

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“…9 Table 1 shows the calculated thickness of the hydrogen target for the above-described modes of operation and also gives the 8 Repurposed from the OLYMPUS experiment 9 During a longer, data-taking run, these pumps would be removed from the beamline. thickness of the gas targets used in the PRad [22] and OLYM-PUS [23] experiments. Our lowest gas thickness is comparable with that used in the PRad experiment, and almost 3 orders of magnitude larger than in the OLYMPUS experiment.…”

Section: Operation At Jlabmentioning

confidence: 99%

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Design and operation of a windowless gas target internal to a solenoidal magnet for use with a megawatt electron beam

Lee

Corliss

Friščić

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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A windowless hydrogen gas target of nominal thickness 10 19 cm −2 is an essential component of the DarkLight experiment, which is designed to utilize the megawatt electron beam at an Energy Recovery Linac (ERL). The design of such a target is challenging because the pressure drops by many orders of magnitude between the central, high-density section of the target and the surrounding beamline, resulting in laminar, transitional, and finally molecular flow regimes. The target system was assembled and operated at Jefferson Lab's Low Energy Recirculator Facility (LERF) in 2016, and subsequently underwent several revisions and calibration tests at MIT Bates in 2017. The system at dynamic equilibrium was simulated in COMSOL to provide a better understanding of its optimal operation at other working points. We have determined that a windowless gas target with sufficiently high density for DarkLight's experimental needs is feasible in an ERL environment.

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Section: Operation At Jlabmentioning

confidence: 99%

“…Thickness of the DarkLight gas target at pressures of 0.408, 1.35 and 3.43 mbar at room temperature, assuming an effective target length of 60 cm with comparison to the target thickness in the PRad[22] and the OLYMPUS[23] experiments.…”

mentioning

confidence: 99%

Design and operation of a windowless gas target internal to a solenoidal magnet for use with a megawatt electron beam

Lee

Corliss

Friščić

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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“…The DORIS beam was directed through a windowless hydrogen gas target that was internal to the ring vacuum [31]. A differential pumping system of six turbomolecular vacuum pumps was necessary to continuously remove the hydrogen gas that flowed from the ends of the target and prevent it from spoiling the ring vacuum.…”

Section: The Olympus Experimentsmentioning

confidence: 99%

The continuing story of two-photon exchange: results from the OLYMPUS experiment

Schmidt¹

2017

Proceedings of 55th International Winter Meeting on Nuclear Physics — PoS(BORMIO2017)

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Over the past two decades, a discrepancy has emerged between two different techniques for measuring the proton's electromagnetic form factors. Unpolarized electron-proton cross section measurements paint a picture of the proton's internal structure that is incompatible with measurements from polarization transfer experiments. The leading hypothesis is that the discrepancy is caused by a typically neglected radiative correction, hard two-photon exchange (TPE), which would affect the two measurement techniques in different ways. There is no model independent way to calculate hard TPE, but it can be measured experimentally by looking for an asymmetry between the positron-proton and electron-proton elastic cross sections. Three recent experiments have attempted to quantify this asymmetry, and, just last month, the third of these, called OLYMPUS, released its results [1]. The OLYMPUS experiment collected data in 2012 at DESY, alternating between 2 GeV electron and positron beams, directed through a hydrogen gas target. The scattered lepton and recoiling proton were detected in coincidence with a large acceptance toroidal spectrometer. The relative luminosity between the two beam species was monitored with three independent systems, and the results comprise 3 inverse fb of integrated luminosity, exceeding by a factor of three the other two TPE experiments combined. In this talk, the case for the TPE hypothesis will be presented, the OLYMPUS experiment will be described, and the results of all three experiments will be compared.

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“…The OLYMPUS experiment [26,[28][29][30] aims to precisely measure the ratio of elastic e + p and e − p scattering cross sections to better than 1% total error for a beam energy of 2 GeV and a wide range of scattering angles. In the kinematic region covered by OLYMPUS the cross section ratio is expected to deviate from unity by as much as 5-10%, if the form factor discrepancy between Rosenbluth and recoil polarization measurements is caused by two-photon exchange.…”

Section: The Olympus Experimentsmentioning

confidence: 99%

EM Form Factors and OLYMPUS

Köhl

2014

EPJ Web of Conferences

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Abstract. The elastic form factors of the nucleon characterize the distributions of charge and magnetization in momentum space and are important input for calculations of strong interaction phenomena and nuclear structure. The dramatic discrepancy in the observed ratio of elastic proton form factors between the Rosenbluth separation and polarization transfer methods has invoked numerous theoretical and experimental investigations. The previously neglected effect from two-photon exchange has become the favored explanation for the discrepancy. While the effect can not be calculated from first principles, it can be verified experimentally in several ways, most stringently by comparing the positronproton and electron-proton elastic cross sections. The OLYMPUS experiment at DESY has been carried out to quantify the effect of two-photon exchange using intense stored positron and electron beams along with an internal unpolarized hydrogen target and a large acceptance detector to measure the ratio of the positron-proton and electron-proton elastic scattering cross sections. The status of proton form factor measurements and of the experimental efforts to verify the effect of two-photon exchange is presented, with some emphasis on the OLYMPUS experiment.

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The OLYMPUS internal hydrogen target

Cited by 21 publications

References 6 publications

Design and operation of a windowless gas target internal to a solenoidal magnet for use with a megawatt electron beam

Design and operation of a windowless gas target internal to a solenoidal magnet for use with a megawatt electron beam

The continuing story of two-photon exchange: results from the OLYMPUS experiment

EM Form Factors and OLYMPUS

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