The TRIple PLunger for EXotic beams TRIPLEX for excited-state lifetime measurement studies on rare isotopes

Abstract

Expérience NSCLInternational audienceA new device, the TRIple PLunger for EXotic beams (TRIPLEX), has been developed for lifetime measurement studies with rare isotope beams. This plunger device holds up to three metal foils in the beam path and facilitates the recoil distance Doppler-shift technique to measure lifetimes of nuclear excited states in the range of 1 ps to 1 ns. The unique design allows independent movement of the target and the second degrader with respect to a fixed first degrader in between, enabling advanced experimental approaches, such as the differential recoil distance method and the double recoil distance method. The design and control of the device are presented in this paper, together with simulated performances of the new applications. As an example of actual experiments, results from the lifetime measurement of the neutron-rich $^{17}$C isotope performed at the National Superconducting Cyclotron Laboratory are shown

Lifetime measurement of the41+state ofNi58with the recoil distance method

“…The secondary 74 Kr beam at 93 MeV per nucleon had an intensity averaging at 1 × 10 5 particles per second with a purity of approximately 40%. The secondary beam was then sent to the experimental area, where lifetime measurements were performed with the Triple PLunger for EXotic Beams (TRIPLEX) [23] coupled with GRETINA [24] and the S800 spectrograph [27].…”

“…The TRIPLEX [23] is a device which enables sensitive lifetime measurements based on the recoil distance method by the placement of up to three foils into the beam line. The first foil was a 750 µm 9 Be target foil.…”

Isomeric Character of the Lowest Observed 4+ State in S44Parker1, Wiedenhöver2, Cottle3 et al. 2017Phys. Rev. Lett.Self Cite201230View full textAdd to dashboardCite

“…We populate this state via two-proton knockout from a beam of exotic 46 Ar projectiles and measure its lifetime using the recoil distance method with the GRETINA γ-ray spectrometer. The result, 76 (14)stat(20)sys ps, implies a hindered transition of B(E2; 4 + → 2 + 1 ) = 0.61(19) singleparticle or Weisskopf units (W.u.) strength and supports the interpretation of the 4 + state as a K=4 isomer, the first example of a high-K isomer in a nucleus of such low mass.…”

“…At the target location of GRETINA, we used a plunger apparatus [14], which held the 0.5 mm thick 9 Be target at an adjustable distance from a 1 mm thick Nb degrader and also a thin plastic stripper foil to equilibrate the charge-state distribution of reaction residues. The recoildistance method allows us to determine the lifetime of excited nuclear states by identifying the γ-rays emitted before and after the recoiling nucleus passes the degrader by detecting their differently Doppler-shifted laboratorysystem energies.…”

Lifetime measurements ofC17excited states and three-body and continuum effects

“…In order to overcome these limitations, we have employed the GRETINA array to exploit excellent efficiency and resolution for in-beam γ-ray spectroscopy. We have also developed a new plunger device, the TRIple PLunger for EXotic beams (TRIPLEX) [31]. The new plunger design incorporates a target and two degrader foils allowing independent movement of the target and second degrader with respect to a fixed degrader in the middle.…”