Clover Detectors Research Articles

The (Li6,Li*6[3.56MeV]) reaction at 100 MeV/u as a probe of Gamow-Teller transition strengths in the inelastic scattering channel

Background: Inelastic neutrino-nucleus scattering is important for understanding core-collapse supernovae and the detection of emitted neutrinos from such events in earth-based detectors. Direct measurement of the cross sections is difficult and has only been performed on a few nuclei. It is, therefore, important to develop indirect techniques from which the inelastic neutrino-nucleus scattering cross sections can be determined. Purpose: This paper presents a development of the (Li-6,Li-6*[T = 1, T-z = 0, 0(+), 3.56 MeV]) reaction at 100 MeV/u as a probe for isolating the isovector spin-transfer response in the inelastic channel (Delta S = 1, Delta T = 1, Delta T-z = 0) from which the Gamow-Teller transition strengths from nuclei of relevance for inelastic neutrino-nucleus scattering cross sections can be extracted. Method: By measuring the Li-6 ejectile in a magnetic spectrometer and selecting events in which the 3.56 MeV gamma ray from the decay of the Li-6*[3.56 MeV] state is detected, the isovector spin-transfer selectivity is obtained. High-purity germanium clover detectors served to detect the gamma rays. Doppler reconstruction was used to determine the gamma energy in the rest frame of Li-6. From the Li-6 and 3.56 MeV gamma-momentum vectors the excitation energy of the residual nucleus was determined. Results: In the study of the C-12(Li-6,Li-6*[3.56 MeV]) reaction, the isovector spin-transfer excitation-energy spectrum in the inelastic channel was successfully measured. The strong Gamow-Teller state in C-12 at 15.1 MeV was observed. Comparisons with the analog C-12(Li-6,He-6) reaction validate the method of extracting the Gamow-Teller strength. In measurements of the Mg-24, Nb-93(Li-6,Li-6*[3.56 MeV]) reactions, the 3.56 MeV gamma peak could not be isolated from the strong background in the gamma spectrum from the decay of the isoscalar excitations. It is argued that by using a gamma-ray tracking array instead of a clover array, it is feasible to extend the mass range over which the (Li-6,Li-6*) reaction can be used for extracting the isovector spin-transfer response up to mass numbers of similar to 25 and perhaps higher. Conclusions: It is demonstrated that the (Li-6,Li-6*[3.56 MeV]) reaction probe can be used to isolate the inelastic isovector spin-transfer response in nuclei. Application to nuclei with mass numbers of about 25 or more, however, will require a more efficient gamma-ray array with a better tracking capability.

High spin states in 63Cu

High-spin states in 63Cu were investigated through in-beam $\gamma$ -ray spectroscopic techniques using the 52Cr(18O, $\alpha$ p2n) fusion-evaporation reaction at a beam energy of 72.5 MeV. The $\gamma$ -rays emitted by the excited nucleus were recorded in the coincidence mode using fourteen Compton suppressed Ge clover detectors of the Indian National Gamma-ray Array (INGA). Based on the $\gamma$ - $\gamma$ coincidence data, twenty-one new $\gamma$ -ray transitions have been observed and placed --thereby extending the level scheme of 63Cu up to spin $25/2\hbar$ and excitation energy $\sim 8.36$ MeV. Shell model calculations are performed in the $f_{5/2}pg_{9/2}$ model space with a 56Ni core using two effective interactions, viz. JUN45 and jj44b to interpret the observed excited states of this nucleus. A reasonable agreement is found between the experimental finding and the shell-model calculations --which implies that the excitations within the $f_{5/2}p_{3/2}p_{1/2}$ orbitals are more dominant in defining the observed level structure than the excitation across the magic shell gap $N = Z = 28$ .

A Compton suppressed detector multiplicity trigger based digital DAQ for gamma-ray spectroscopy

The development of a digitizer based pulse processing and data acquisition system for γ-ray spectroscopy with large detector arrays is presented. The system is based on 250 MHz 12-bit digitizers, and is triggered by a user chosen multiplicity of Compton suppressed detectors. The logic for trigger generation is similar to the one practised for analog (NIM/CAMAC) pulse processing electronics, while retaining the fast processing merits of the digitizer system. Codes for reduction of data acquired from the system have also been developed. The system has been tested with offline studies using radioactive sources as well as in the in-beam experiments with an array of Compton suppressed Clover detectors. The results obtained therefrom validate its use in spectroscopic efforts for nuclear structure investigations.

Correction of coincidence summing effects for add-back mode measurements with a 4π clover detector using experimental total efficiency

We demonstrated coincidence summing corrections for the measured spectra of multi γ-ray emitters with the add-back mode of a 4π clover detector with an almost 98% solid angle condition using a Monte Carlo calculation based on nuclear decay data. The total and peak efficiencies were determined by Monte Carlo simulation code GEANT4 so that the experimental efficiencies measured mono/quasi-mono energetic γ-ray sources of 109Cd, 139Ce, 137Cs, 54Mn, 57, 60Co and 88Y may be reproduced well. Under a large solid angle condition, (i.e., a large coincidence summing condition), the corrected peak efficiencies, deduced from 134Cs and 152,154Eu measured, were in agreement within 5% with peak efficiencies in the absence of coincidence summing. The coincidence summing effects were corrected properly according to the decay scheme information, using experimental and simulated values of the total efficiency. We thus demonstrated the effectiveness of measurement with the add-back mode of the detector for γ-ray spectroscopy.

Multiple band structures in Ge70

High-spin states in $^{70}\mathrm{Ge}$ were studied using the $^{55}\mathrm{Mn}$($^{18}\mathrm{O},p2n$) fusion-evaporation reaction at a beam energy of 50 MeV. Prompt $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences were measured using the Florida State University Compton-suppressed Ge array consisting of three Clover detectors and seven single-crystal detectors. An investigation of these coincidences resulted in the addition of 31 new transitions and the rearrangement of four others in the $^{70}\mathrm{Ge}$ level scheme, providing a more complete picture of the high-spin decay pattern involving both positive- and negative-parity states with multiple band structures. Spins were assigned based on directional correlation of oriented nuclei ratios, which many times also led to unambiguous parity determinations based on the firm assignments for low-lying states made in previous work. Total Routhian surface calculations, along with the observed trends in the experimental kinematic moment of inertia with rotational frequency, support the multiquasiparticle configurations of the various crossing bands proposed in recent studies. The high-spin excitation spectra predicted by previous shell-model calculations compare favorably with the experimental one determined from this study.

Evolution of $\gamma $ Collectivity --- $(n,\gamma )$ Spectroscopy of $^{98}$Mo with FIPPS

Excited states in 98Mo have been populated in (n,γ) reaction and studied using γ-ray coincidences measured with Germanium Clover detectors of the new instrument FIPPS. The aim of the study is to investigate the evolution of γ collectivity in Mo isotopes in its early-development stage. The ground state of 97Mo 5/2+ should allow the observation of the γ band in 98Mo up to spin 7+. This is sufficient to measure interesting properties of the γ band, such as mixing ratios.

EXILL—a high-efficiency, high-resolution setup for γ-spectroscopy at an intense cold neutron beam facility

In the EXILL campaign a highly efficient array of high purity germanium (HPGe) detectors was operated at the cold neutron beam facility PF1B of the Institut Laue-Langevin (ILL) to carry out nuclear structure studies, via measurements of γ-rays following neutron-induced capture and fission reactions. The setup consisted of a collimation system producing a pencil beam with a thermal capture equivalent flux of about 108 n s−1cm−2 at the target position and negligible neutron halo. The target was surrounded by an array of eight to ten anti-Compton shielded EXOGAM Clover detectors, four to six anti-Compton shielded large coaxial GASP detectors and two standard Clover detectors. For a part of the campaign the array was combined with 16 LaBr3:(Ce) detectors from the FATIMA collaboration. The detectors were arranged in an array of rhombicuboctahedron geometry, providing the possibility to carry out very precise angular correlation and directional-polarization correlation measurements. The triggerless acquisition system allowed a signal collection rate of up to 6 × 105 Hz. The data allowed to set multi-fold coincidences to obtain decay schemes and in combination with the FATIMA array of LaBr3:(Ce) detectors to analyze half-lives of excited levels in the pico- to microsecond range. Precise energy and efficiency calibrations of EXILL were performed using standard calibration sources of 133Ba, 60Co and 152Eu as well as data from the reactions 27Al(n,γ)28Al and 35Cl(n,γ)36Cl in the energy range from 30 keV up to 10 MeV.

Prompt-delayed $\gamma$ γ -ray spectroscopy with AGATA, EXOGAM and VAMOS++

A new experimental setup to measure prompt-delayed $\gamma$ -ray coincidences from isotopically identified fission fragments, over a wide time range of 100ns-200μ s, is presented. The fission fragments were isotopically identified, on an event-by-event basis, using the VAMOS++ large acceptance spectrometer. The prompt $\gamma$ rays emitted at the target position and corresponding delayed $ \gamma$ rays emitted at the focal plane of the spectrometer were detected using, respectively, thirty two crystals of the AGATA $\gamma$ -ray tracking array and seven EXOGAM HPGe Clover detectors. Fission fragments produced in fusion and transfer-induced fission reactions, using a 238U beam at an energy of 6.2 MeV/u impinging on a 9Be target, were used to characterize and qualify the performance of the detection system.

Investigation of antimagnetic rotation in 101Pd

Excited states in the 101Pd isotope were investigated following the 75As(31P, )101Pd reaction at Elab = 125 MeV. In-beam γ-ray measurements were performed using the Indian National Gamma Array (INGA) spectrometer consisting of 21 Compton-suppressed clover detectors. Level lifetimes have been measured for the negative-parity band in 101Pd using the Doppler-shift attenuation method up to the 43/2− state and are found to differ substantially from the recently reported values. The deduced quadrupole transition rates exhibit a monotonically decreasing behaviour with increasing angular momentum in the spin range along with large / values (>300 ). Using the semiclassical particle-rotor model, the observed band characteristics are interpreted as antimagnetic rotation based on the ⨂ configuration. The configuration assignment is also favoured by the cranking shell model calculations.

Shape evolution with increasing angular momentum in the Ga66 nucleus

The high-spin nuclear structure of the odd-odd $^{66}\mathrm{Ga}$ nucleus was probed using heavy-ion induced fusion-evaporation reaction. The de-exciting $\ensuremath{\gamma}$ rays were detected by using the Indian National Gamma Array (INGA) consisting of high resolution Compton suppressed clover detectors. The level scheme of $^{66}\mathrm{Ga}$ was extended up to an excitation energy $({E}_{x})$ of $\ensuremath{\sim}10.6$ MeV with spin parity of ${21}^{(+)}$. Two new quadrupole bandlike structures, one positive and one negative parity, based on the states having spin parity of ${J}^{\ensuremath{\pi}}={11}^{+}$ and ${10}^{\ensuremath{-}}$, respectively, were found. The experimental energy levels are compared with calculations within the framework of shell model calculation using $jj44bpn$ effective interaction. The agreement between experiment and theory is good. The total Routhian surface calculations were performed to understand the shape of the $^{66}\mathrm{Ga}$ nucleus associated with the configurations $\ensuremath{\nu}({g}_{9/2}){}^{3}\phantom{\rule{0.16em}{0ex}}\ensuremath{\nu}({f}_{5/2}){}^{2}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({g}_{9/2}){}^{1}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({f}_{5/2}){}^{2}$ and $\ensuremath{\nu}({g}_{9/2}){}^{2}\phantom{\rule{0.16em}{0ex}}\ensuremath{\nu}({f}_{5/2}){}^{1}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({g}_{9/2}){}^{1}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({f}_{5/2}){}^{2}$ assigned to the positive and negative parity bands, respectively. In the frequency domain $\ensuremath{\omega}=0.20\text{--}0.30$ MeV, both the negative and positive parity quadrupole structures, favor prolate deformation whereas at $\ensuremath{\omega}=0.50$ MeV there is a sudden change to noncollective oblate shape in both the bands.

Conceptual design of a hybrid neutron-gamma detector for study of β-delayed neutrons at the RIB facility of RIKEN

The conceptual design of the BRIKEN neutron detector at the radioactive ion beam factory (RIBF) of the RIKEN Nishina Center is reported. The BRIKEN setup is a complex system aimed at detecting heavy-ion implants, β particles, γ rays and β-delayed neutrons. The whole setup includes the Advanced Implantation Detection Array (AIDA), two HPGe Clover detectors and up to 166 3He-filled counters embedded in a high-density polyethylene moderator. The design is quite complex due to the large number and different types of 3He-tubes involved and the additional constraints introduced by the ancillary detectors for charged particles and γ rays. This article reports on a novel methodology developed for the conceptual design and optimisation of the 3He-counter array, aiming for the best possible performance in terms of neutron detection. The algorithm is based on a geometric representation of two selected detector parameters of merit, namely, the average neutron detection efficiency and the efficiency flatness as a function of a reduced number of geometric variables. The response of the neutron detector is obtained from a systematic Monte Carlo simulation implemented in GEANT4. The robustness of the algorithm allowed us to design a versatile detection system, which operated in hybrid mode includes the full neutron counter and two clover detectors for high-precision gamma spectroscopy. In addition, the system can be reconfigured into a compact mode by removing the clover detectors and re-arranging the 3He tubes in order to maximize the neutron detection performance. Both operation modes shows a rather flat and high average efficiency. In summary, we have designed a system which shows an average efficiency for hybrid mode (3He tubes + clovers) of 68.6% and 64% for neutron energies up to 1 and 5 MeV, respectively. For compact mode (only 3He tubes), the average efficiency is 75.7% and 71% for neutron energies up to 1 and 5 MeV, respectively. The performance of the BRIKEN detection system has been also quantified by means of Monte Carlo simulations with different neutron energy distributions.

The hyperion particle-γ detector array

Hyperion is a new high-efficiency charged-particle γ-ray detector array which consists of a segmented silicon telescope for charged-particle detection and up to fourteen high-purity germanium clover detectors for the detection of coincident γ rays. The array will be used in nuclear physics measurements and Stockpile Stewardship studies and replaces the STARLiTeR array. This article discusses the features of the array and presents data collected with the array in the commissioning experiment.

Measurement of picosecond lifetimes in neutron-rich Xe isotopes

Background: Lifetimes of nuclear excited states in fission fragments have been studied in the past following isotope separation, thus giving access mainly to the fragments’ daughters and only to long-lived isomeric states in the primary fragments. For the first time now, short-lived excited states in the primary fragments, produced in neutron-induced prompt fission of 235U and 241Pu, were studied within the EXILL&FATIMA campaign at the intense neutron-beam facility of the Institute Laue-Langevin in Grenoble. Purpose: We aim to investigate the quadrupole collective properties of neutron-rich even-even 138,140,142Xe isotopes lying between the double shell closure N = 82 and Z = 50 and a deformed region with octupole collectivity. Method: The γ rays emitted from the excited fragments were detected with a mixed array consisting of 8 HPGe EXOGAM Clover detectors (EXILL) and 16 LaBr3(Ce) fast scintillators (FATIMA). The detector system has the unique ability to select the interesting fragment making use of the high resolution of the HPGe detectors and determine subnanosecond lifetimes using the fast scintillators. For the analysis the generalized centroid difference method was used. Results: We show that quadrupole collectivity increases smoothly with increasing neutron number above the closed N = 82 neutron shell. Our measurements are complemented by state-of-the-art theory calculations based on shell-model descriptions. Conclusions: The observed smooth increase in quadrupole collectivity is similar to the evolution seen in the measured masses of the xenon isotopic chain and is well reproduced by theory. This behavior is in contrast to higher Z even-even nuclei where abrupt change in deformation occurs around N = 90.

Characteristics of GRIFFIN high-purity germanium clover detectors

The Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei, GRIFFIN, is a new experimental facility for radioactive decay studies at the TRIUMF-ISAC laboratory. The performance of the 16 high-purity germanium (HPGe) clover detectors that will make up the GRIFFIN spectrometer is reported. The energy resolution, efficiency, timing resolution, crosstalk and preamplifier properties of each crystal were measured using a combination of analog and digital data acquisition techniques. The absolute efficiency and add-back factors are determined for the energy range of 80–3450keV. The detectors show excellent performance with an average over all 64 crystals of a FWHM energy resolution of 1.89(6)keV and relative efficiency with respect to a 3in.×3in. NaI detector of 41(1)% at 1.3MeV.

First observation of low-energyγ-ray enhancement in the rare-earth region

The {\gamma}-ray strength function and level density in the quasi-continuum of 151,153Sm have been measured using BGO shielded Ge clover detectors of the STARLiTeR system. The Compton shields allow for an extraction of the {\gamma} strength down to unprecedentedly low {\gamma} energies of about 500 keV. For the first time an enhanced low- energy {\gamma}-ray strength has been observed in the rare-earth region. In addition, for the first time both the upbend and the well known scissors resonance have been observed simultaneously for the same nucleus. Hauser-Feshbach calculations show that this strength enhancement at low {\gamma} energies could have an impact of 2-3 orders of magnitude on the (n,{\gamma}) reaction rates for the r-process nucleosynthesis.

Geant4 simulation study of Indian National Gamma Array at TIFR

A Geant4 simulation code for the Indian National Gamma Array (INGA) consisting of 24 Compton suppressed clover high purity germanium (HPGe) detectors has been developed. The calculated properties in the energy range that is of interest for nuclear γ-ray spectroscopy are spectral distributions for various standard radioactive sources, intrinsic peak efficiencies and peak-to-total (P/T) ratios in various configurations such as singles, add-back and Compton suppressed mode. The principle of operation of the detectors in add-back and Compton suppression mode have been reproduced in the simulation. The reliability of the calculation is checked by comparison with the experimental data for various γ-ray energies up to 5 MeV. The comparison between simulation results and experimental data demonstrate the need of incorporating the exact geometry of the clover detectors, Anti-Compton Shield and other surrounding materials in the array to explain the detector response to the γ-ray. Several experimental effects are also investigated. These include the geometrical correction to angular distribution, crosstalk probability and the impact of heavy metal collimators between the target and the array on the P/T ratio.

34 - Short-lived Positron Emitters in Beam-on PET Imaging During Proton Therapy

Positron emission tomography is so far the only method for in-vivo dose delivery verification in hadron therapy that is in clinical use. PET imaging during irradiation maximizes the number of detected counts and minimizes washout. In such a scenario, also short-lived positron emitters will be observed. As very little is known on the production of these nuclides, we determined which ones are relevant for proton therapy treatment verification. In order to be relevant, nuclides have to be produced close to the distal edge and thus at rather low proton energy. Therefore we measured the integral production of short-lived positron emitters in the stopping of 55 MeV protons in carbon, oxygen, phosphorus and calcium. The experiments were performed at the irradiation facility of the AGOR cyclotron at KVI-Center for Advanced Radiation Technology, University of Groningen. The positron emitters were identified based on their half-life. In order to do this, the proton beam was pulsed, i.e. delivered as a succession of beam-on and beam-off periods, and the time evolution of the 511 keV positron annihilation photons was recorded. A half-life analysis of the beam-off period allowed to determine the production rates of separate nuclides. The 511 keV photons were detected by a germanium clover detector [1]. A correction for the escape of positrons from the target, determined via Monte Carlo simulations, was applied. In the stopping of 55 MeV protons, the most copiously produced short-lived nuclides and their production rates relative to the relevant long-lived nuclides are: 12N (T1/2 = 11 ms) on carbon (9% of the 11C production), 29P (T1/2 = 4.1 s) on phosphorus (20% of the 30P production) and 38mK (T1/2 = 0.92 s) on calcium (113% of the 38gK production). No short-lived nuclides are produced on water (i.e. oxygen). The experimental production rates are used to calculate the production on PMMA and a representative set of 4 tissue materials. [fig. 1] The number of decays per 55 MeV proton stopped in these materials, integrated over an irradiation, is calculated as function of the duration of the irradiation. The most noticeable result is that for an irradiation in (carbon-rich) adipose tissue, 12N will dominate the PET image up to an irradiation duration of 70 s. On bone tissue, 15O dominates over 12N after 8-15 s (depending on the carbon-to-oxygen ratio). Considering nuclides created on phosphorus and calcium, the short-lived ones provide 2.5 times more decays than the long-lived ones during a 70 s irradiation. Bone tissue will thus be better visible in beam-on PET compared to PET imaging after an irradiation. The results warrant detailed investigations into the energy-dependent production of 12N, 29P and 38mK and their effect on PET imaging during proton irradiations.

Lifetime Measurments of Excited States in Neutron-rich Fission Fragments

Lifetimes of short-lived excited states in a wide range of neutron-rich fission fragments were measured using the recoil distance Doppler shift (RDDS) technique, which was applied to fusion-fission reactions in inverse kinematics for the first time. The fission fragments were identified eventby- event in mass, charge, and atomic number using the VAMOS magnetic spectrometer at GANIL. Gamma rays originating from the fission fragments were measured with the EXOGAM array of Ge Clover detectors around the target position. Using a degrader, the change in the Doppler shift of the $\gamma$ ray allows the application of the RDDS method. Details of the experimental technique will be discussed and the status for the ongoing analysis for odd-mass yttrium isotopes will be presented.

Coexisting single-particle and collective excitations inAs70

High-spin states in $^{70}\mathrm{As}$ were studied using the $^{55}\mathrm{Mn}(^{18}\mathrm{O},3n)$ fusion-evaporation reaction at a beam energy of 50 MeV. Prompt $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences were measured using the Florida State University Compton-suppressed Ge array consisting of three Clover detectors and seven single-crystal detectors. A reinvestigation of the known level scheme resulted in the addition of 32 new transitions and the rearrangement of 10 others. The high-spin decay pattern of yrast negative-parity states was modified and enhanced extensively. Spins were assigned based on directional correlation of oriented nuclei ratios. Lifetimes of seven excited states were measured using the Doppler-shift attenuation method. The $B(E2)$ rates inferred from the lifetimes of states in the yrast positive-parity band imply substantial collectivity, in agreement with the results of previous studies. Substantial signature splitting and large alternations in the $B(M1)$ strengths were observed in this band as well, supporting the interpretation of an aligned $\ensuremath{\pi}{g}_{9/2}\ensuremath{\bigotimes}\ensuremath{\nu}{g}_{9/2}$ intrinsic configuration for this structure beginning at the lowest ${9}^{+}$ state. Large-scale shell-model calculations performed for $^{70}\mathrm{As}$ reproduce the relative energy differences between adjacent levels and the $B(M1)$ rates in the yrast positive-parity band rather well, but underestimate the $B(E2)$ strengths. The ${g}_{9/2}$ orbital occupancies for the lowest ${9}^{+}$ state predicted by the shell-model calculations provide additional evidence of a stretched $\ensuremath{\pi}{g}_{9/2}\ensuremath{\bigotimes}\ensuremath{\nu}{g}_{9/2}$ configuration for this state.

Improved measurement of the half-life of theJπ=8−nuclear isomerEu152m2

The standard $\ensuremath{\gamma}$-ray energy calibration source $^{152}\mathrm{Eu}$ is well known based on the 13.5 y decay of its ground state. However, in addition to this decay $^{152}\mathrm{Eu}$ also has two relatively long-lived isomeric states: a 9 h ${J}^{\ensuremath{\pi}}={0}^{\ensuremath{-}}$ state at ${E}^{*}=46$ keV and a 96 min ${J}^{\ensuremath{\pi}}={8}^{\ensuremath{-}}$ state at ${E}^{*}=148$ keV. Here we report a new measurement of the half-lives of both of these isomeric states. Excited states in $^{152}\mathrm{Eu}$ were populated following the $^{154}\mathrm{Sm}(p,3n)$ reaction using a 25 MeV proton beam from the K-150 cyclotron at the Cyclotron Institute of Texas A University. Post irradiation, $\ensuremath{\gamma}$ rays from the de-excitation of the long lived isomeric states were measured using the six BGO shielded high-purity germanium (HPGe) clover detectors that are part of the STARLiTeR array. The half-life of the ${J}^{\ensuremath{\pi}}={8}^{\ensuremath{-}}$ isomer $^{152{m}_{2}}\mathrm{Eu}$ was obtained by measuring the decrease in intensity of the 90 keV $\ensuremath{\gamma}$ ray from the cascade to the ground state. The half-life of this state was measured to be 95.8(4) min which is in agreement with and significantly more precise than the previously measured value of 96(1) min. In a manner similar to the ground state the second long-lived isomer $^{151{m}_{1}}\mathrm{Eu}$, the ${J}^{\ensuremath{\pi}}={0}^{\ensuremath{-}}$ state at 46 keV, $\ensuremath{\beta}$ decays to excited states in $^{152}\mathrm{Gd}$ and $^{152}\mathrm{Sm}$. The half-life of this state was measured to be 9.39(7) h using five $\ensuremath{\gamma}$-ray transitions.