Research opportunities at the upgraded HIγS facility

Weller, H. R.; Ahmed, M. W.; H, Gao; Tornow, W.; Wu, Y.; Gai, M.; Miskimen, R.

doi:10.1016/j.ppnp.2008.07.001

Cited by 403 publications

(263 citation statements)

References 168 publications

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“…We are planning to use this active-target technique at the LCB γ-ray facilities of HIγS, TUNL, Durham, USA [6] and ELI-NP, Magurele, Romania [7]. The advantages of this active-target system include good timing and position resolution, high rate capability, detection and identification of both photodisintegration fragments, and insensitivity to the electromagnetic background.…”

Section: Discussionmentioning

confidence: 99%

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Active Oxygen Target for Studies in Nuclear Astrophysics with Laser Compton Backscattered γ-ray Beams

et al. 2018

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An active target is being developed to be used in low-energy nuclear astrophysics experiments. It is a position-and time-sensitive detector system based on the low-pressure Multi Wire Proportional Chamber (MWPC) technique. Methylal ((OCH 3 ) 2 CH 2 ), at a pressure of a few Torr, serves as the working gas for MWPC operation, and in addition, the oxygen atoms of the methylal molecules serve as an experimental target. The main advantage of this new target detector system is that it has high sensitivity to the low-energy, highly-ionizing particles produced after photodisintegration of 16 O and insensitivity to γ-rays and minimum ionizing particles. This allows users to detect only the products of the nuclear reaction of interest. The threshold energies for detection of α particles and 12 C nuclei are about 50 keV and 100 keV, respectively. The main disadvantage of this detector is the small target thickness, which is around a few tens of µg/cm 2 . However, reasonable luminosity can be achieved by using a multimodule detector system and an intense, Laser Compton Backscattered (LCB) γ-ray beam. This paper summarizes the architecture of the active target and reports test results of the prototype detector. The tests investigated the timing and position resolutions of 30 × 30 mm 2 low-pressure MWPC units using an α-particle source. The possibility of measuring the 16 O(γ, α) 12 C cross-section in the 8-10 MeV energy region by using a LCB γ-ray beam is also discussed. A measurement of the 16 O(γ, α) 12 C cross-section will enable the reaction rate of 12 C(α, γ) 16 O to be determined with significantly improved precision compared to previous experiments.

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Section: Discussionmentioning

confidence: 99%

“…One is based on the bubble chamber technique and a bremsstrahlung photon beam [3]; the other employs an Optical Time Projection Chamber (O-TPC) [4] and a Laser Compton Backscattered (LCB) γ-ray beam [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Active Oxygen Target for Studies in Nuclear Astrophysics with Laser Compton Backscattered γ-ray Beams

et al. 2018

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“…The High Intensity γ-ray Source at the Triangle Universities Nuclear Laboratory (TUNL) at the Duke University is perfectly suited to perform NRF experiments on stable nuclei [16,18]. HIγS provides a high intensity (> 50 γ/eV/s) polarized photon beam with a narrow energy spread (≈3%) and a variable energy (1 MeV to currently 100 MeV).…”

Section: Methodsmentioning

confidence: 99%

The high-efficiency spectroscopy setup at

Löher¹,

Derya²,

Aumann³

et al. 2013

Nuclear Instruments and Methods in Physics Research Section A:

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The existing Nuclear Resonance Fluorescence (NRF) setup at the HIγS facility at the Triangle Universities Nuclear Laboratory at Duke University has been extended in order to perform γ-γ coincidence experiments. The new setup combines large volume LaBr 3 :Ce detectors and high resolution HPGe detectors in a very close geometry to offer high efficiency, high energy resolution as well as high count rate capabilities at the same time. The combination of a highly efficient γ-ray spectroscopy setup with the mono-energetic high-intensity photon beam of HIγS provides a worldwide unique experimental facility to investigate the γ-decay pattern of dipole excitations in atomic nuclei. The performance of the new setup has been assessed by studying the nucleus 32 S at 8.125 MeV beam energy. The relative γ-decay branching ratio from the 1 + level at 8125.4 keV to the first excited 2 + state was determined to 15.7(3) %.

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“…The current measurement of the 12 C(γ, 3α) reaction was performed at the HIγS facility that produces an intense, nearly monoenergetic gamma-ray beam by Compton backscattering photons from a free-electron laser [13]. Beam energy spreads of 300 -350 keV were measured at beam energies between 9.1 and 10.7 MeV, with on-target intensities of ≈ 2 × 10 8 γ/sec.…”

Section: Measurement Of the 1c(γ 3α) Reactionmentioning

confidence: 99%

The structure of the Hoyle state and its 2⁺partner state in¹²C

Gai

2012

EPJ Web of Conferences

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Abstract. We have measured the 12 C(γ, 3α) reaction with an Optical Time Projection Chamber (O-TPC) detector operating with the CO 2 (80%) + N 2 (20%) gas mixture and gamma-ray beams from the HIγS facility of the TUNL at Duke. We measured complete angular distributions (between 9.1 -10.7 MeV) from which we determine the cross section yield curve and E1 − E2 relative phases leading to an unambiguous identification of the second 2 + state in 12 C at 10.03(11) MeV. The observed spectrum of 12 C below 12 MeV including the 2 + 2 state observed in this work resembles the rotation-vibration spectrum predicted for a triangular shape oblate spinning top in which the Hoyle state is the first vibrational breathing mode of the triangular three alpha-particle system. We also observed a hint of the 2 + 3 state which is predicted by the U(7) model as a member of the 1 − bending mode band, but the existence of this 2 + 3 is yet to be confirmed. The predicted rotation-vibration spectrum of a triangular shape oblate spinning top (with a D 3h symmetry) allows us to compare the moment of inertia of the predicted Hoyle rotational band to the ground state rotational band and in this way extract the (large) rms radius of the Hoyle state of 3.22(8) fm. We compare the deduced rms radius with recent ab-initio theories and cluster models as well as the radius extracted from 12 C(p, p ) data.

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Research opportunities at the upgraded HIγS facility

Cited by 403 publications

References 168 publications

Active Oxygen Target for Studies in Nuclear Astrophysics with Laser Compton Backscattered γ-ray Beams

Active Oxygen Target for Studies in Nuclear Astrophysics with Laser Compton Backscattered γ-ray Beams

The high-efficiency spectroscopy setup at

The structure of the Hoyle state and its 2⁺partner state in¹²C

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Research opportunities at the upgraded HIγS facility

Cited by 403 publications

References 168 publications

Active Oxygen Target for Studies in Nuclear Astrophysics with Laser Compton Backscattered γ-ray Beams

Active Oxygen Target for Studies in Nuclear Astrophysics with Laser Compton Backscattered γ-ray Beams

The high-efficiency spectroscopy setup at

The structure of the Hoyle state and its 2+partner state in12C

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Product

Resources

About

The structure of the Hoyle state and its 2⁺partner state in¹²C