Polarization-direction Correlation Research Articles

Compton polarimetry with a 36-fold segmented HPGe-detector of the AGATA-type

The calibration of a highly-segmented AGATA-type HPGe-detector as a γ-ray Compton polarimeter and a method for (quasi-)continuous angle Compton polarimetry are presented. The high granularity, combined with the large detection efficiency of the AGATA-type HPGe-crystals, offers a significant advantage for polarization measurements of γ-radiation. A polarization-directional correlation experiment with γ-rays from a 60Co source with an activity of about 680kBq was used to determine the polarization sensitivity of a single AGATA-type HPGe-crystal at 1173 and 1332keV and to demonstrate the method. The polarization measurement was based on segment information. In our set-up a polarization sensitivity of 19% at 1332keV has been achieved.

Seven-quasiparticle bands inCe139

The high spin states in the $^{139}\mathrm{Ce}$ nucleus have been studied by in-beam $\ensuremath{\gamma}$-spectroscopic techniques using the reaction $^{130}\mathrm{Te}(^{12}\mathrm{C},3n)^{139}\mathrm{Ce}$ at ${E}_{\mathrm{beam}}=65$ MeV. A gamma detector array, consisting of five Compton-suppressed Clover detectors was used for coincidence measurements. 15 new levels have been proposed and 28 new $\ensuremath{\gamma}$ transitions have been assigned to $^{139}\mathrm{Ce}$ on the basis of $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidence data. The level scheme of $^{139}\mathrm{Ce}$ has been extended above the known 70 ns ${\frac{19}{2}}^{\ensuremath{-}}$ isomer up to $~6.1$ MeV in excitation energy and $\frac{35}{2}\ensuremath{\hbar}$ in spin. The spin-parity assignments for most of the newly proposed levels have been made using the deduced Directional Correlation from Oriented states of nuclei (DCO ratio) and the Polarization Directional Correlation from Oriented states (PDCO ratio) for the de-exciting transitions. The observed level structure has been compared with a large basis shell model calculation and also with the predictions from cranked Nilsson-Strutinsky (CNS) calculations. A general consistency has been observed between these two different theoretical approaches.

Analytic optical eye diagram evaluation in the presence of polarization-mode dispersion, polarization-dependent loss, and chromatic dispersion in dynamic single-mode fiber communication networks

We report on an exact analytic method to evaluate the optical eye diagram due to polarization-mode dispersion (PMD), polarization-dependent loss (PDL), and chromatic dispersion (CD) in dynamic fiber links for any given optical pulse sequence. With this method we consider all orders of PMD and PDL, and we obtain the time-dependent average output light intensity as well as its corresponding variations. With this method we can obtain accurate impairment evaluations for communication systems due to given PMD, PDL, and CD. Time jitter caused by the PMD and PDL polarization direction correlation is also discussed.

Observation of magnetic rotation in odd-oddAg104

The high spin level structure of $^{104}\text{Ag}$ has been extended to ${I}^{\ensuremath{\pi}}={20}^{+}$ and excitation energy of $7.159\phantom{\rule{0.3em}{0ex}}\text{MeV}$ through the discrete line $\ensuremath{\gamma}$-ray spectroscopy. The negative parity ground state band has been confirmed and extended to ${I}^{\ensuremath{\pi}}={18}^{\ensuremath{-}}$. Two new nonyrast dipole bands, one with positive and the other with negative parity, have been observed. The parities of the two bands have been established through polarization directional correlation measurement of the feed-out transitions from these bands. The level lifetimes have been measured in the ground state band and the positive parity dipole band. The measured total angular momenta and the $B(M1)$ rates have been compared with the predictions of hybrid version of the tilted axis cranking. The $B(M1)$ rates have also been compared with the values obtained from D\onau's geometric formula. The tilted axis calculations give good overall agreement which suggests that all the three bands of $^{104}\text{Ag}$ exhibits magnetic rotation.

Experimental test of the polarization direction correlation method (PDCO)

The study of the polarization direction correlation method (PDCO) for γ quanta emitted from the nuclear states oriented in fusion-evaporation reactions is discussed with emphasis on making unique multipolarity assignments. The method is applied to the data coming from a typical experiment performed with the EUROGAM II array, where polarization-sensitive CLOVER detectors were used. The accuracy obtained in the experiment for the studied transitions was high enough to exclude, using the PDCO method, most of the ambiguities which occur if the assignments are made on the basis of angular correlation measurements alone.

Level spins and multipole mixing ratios of the transitions inMo94

Directional correlations and polarization-directional correlations have been measured for several $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ cascades in $^{94}\mathrm{Mo}$ populated from the decay of $^{94}\mathrm{Tc}^{g}$. NaI(Tl)-Ge(Li) detectors were used in both experiments. Combination of the results of those measurements gives unique spin-parity assignments of ${6}^{+}$ for both the 2872.5 and 3339.5 keV levels. The determined $\frac{E2}{M1}$ mixing ratios are $\ensuremath{\delta}(449)={\ensuremath{-}0.04}_{\ensuremath{-}0.04}^{+0.08}$, $\ensuremath{\delta}(742)=0.65\ifmmode\pm\else\textpm\fi{}0.15$, and $\ensuremath{\delta}(916)=\ensuremath{-}0.04\ifmmode\pm\else\textpm\fi{}0.04$.RADIOACTIVITY $^{94}\mathrm{Tc}$ from $^{93}\mathrm{Nb}(\ensuremath{\alpha},3n)$; measured $\ensuremath{\gamma}\ensuremath{\gamma}(0)$ and $\ensuremath{\gamma}\ensuremath{\gamma}(90 \mathrm{LP})$ (Linearpolarization correlation). Deduced ${J}^{\ensuremath{\pi}}$ $\ensuremath{\delta}(\frac{E2}{M1})$. Ge(Li) and NaI(Tl) detectors.

Spins of the 2350, 2516, and 2547 keV levels inCe140determined fromγ−γdirectional and polarization-directional correlations

Directional correlations and polarization-directional correlations have been measured for different $\ensuremath{\gamma}$ cascades in $^{140}\mathrm{Ce}$, populated from the decay of $^{140}\mathrm{La}$. Combination of Ge(Li) and INa(Tl) detectors were used in both experiments. For the polarization-directional correlation measurement a planar Ge(Li) detector was employed as the linear polarization analyzer. Combination of the results of these measurements gives unique spin assignments of ${5}^{\ensuremath{-}}$, ${4}^{+}$, and ${1}^{+}$ for the 2350, 2516, and 2547 keV levels, respectively. The determined mixing ratios are: $\ensuremath{\delta}(131)=\ensuremath{-}0.33\ifmmode\pm\else\textpm\fi{}0.04$, $\ensuremath{\delta}(267)=0.39\ifmmode\pm\else\textpm\fi{}0.05$, $\ensuremath{\delta}(432)=\ensuremath{-}0.54\ifmmode\pm\else\textpm\fi{}0.10$, $\ensuremath{\delta}(868)=\ensuremath{-}0.034\ifmmode\pm\else\textpm\fi{}0.007$, and $\ensuremath{\delta}=0.10\ifmmode\pm\else\textpm\fi{}0.03$.RADIOACTIVITY $^{140}\mathrm{La}$; measured $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}(\ensuremath{\theta})$ and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}(90\ifmmode^\circ\else\textdegree\fi{}\mathrm{LP})$ (linear polarization correlation) $^{140}\mathrm{Ce}$ deduced $J$, $\ensuremath{\pi}$, $\ensuremath{\delta}$. Ge(Li) detectors.

Spin of the 1248- and 1958-keV levels inTe124determined from gamma-gamma directional and polarization-directional correlations

Directional correlations and polarization-directional correlations have been measured for the 646-603- and 709-646-keV cascades in $^{124}\mathrm{Te}$ populated from the decay of $^{124}\mathrm{Sb}$. Ge(Li) detectors were used in both spectrometers, one of them, a planar Ge(Li) detector as the linear-polarization analyzer for the $\ensuremath{\gamma}$ radiation. Combination of the results of these measurements gives unique spin assignments of ${4}^{+}$ for the 1248- and 1958-keV levels. The determined $\frac{E2}{M1}$ mixing ratios are: $\ensuremath{\delta}(646)=0.00\ifmmode\pm\else\textpm\fi{}0.01$ and $\ensuremath{\delta}(709)={0.02}_{\ensuremath{-}0.07}^{+0.06}$.RADIOACTIVITY $^{124}\mathrm{Sb}$; measured $\ensuremath{\gamma}\ensuremath{\gamma}(\ensuremath{\theta})$ and $\ensuremath{\gamma}\ensuremath{\gamma}(90\ifmmode^\circ\else\textdegree\fi{} \mathrm{LP})$ (linear-polarization correlation), $^{124}\mathrm{Te}$ deduced $I$ $\ensuremath{\delta}(\frac{E2}{M1})$. Ge(Li) detectors.

Negative Parity Levels in 30Si

A polarization direction correlation measurement of γ rays from the 7.044 MeV level in 30Si results in Jπ = 5− for this level and implies a Jπ = 4− assignment for the level at 6.503 MeV. A particle gamma ray coincidence measurement establishes a new decay branch (15 ± 4%) for the 6.503 MeV level to the 5.485 MeV Jπ = 3− level. The Doppler shift attenuation method was used to measure the mean lifetime of the 7.044 MeV level as [Formula: see text]. A simple shell model structure for the low lying negative parity states is presented and shown to be consistent with experimental measurements.

Spins of the levels and multipole mixing ratios of transitions in 125Sb determined from γ-γ directional correlation and polarization-directional correlation measurements

Abstract In order to resolve several discrepancies in spin assignments to levels in 125 Sb, directional correlations and polarization-directional correlations have been measured for several γ-γ cascades in 125 Sb populated from the decay of 125 Sn. Earlier results obtained from using NaI and Ge(Li) and NaI detectors were difficult to interpret due to the complex structure of the decay scheme. To improve the experimental situation, we have used two coaxial Ge(Li) detectors for the angular correlation measurements and a coaxial Ge(Li)-planar Ge(Li) combination for the polarization-directional correlations. Combination of the results of these measurements give unique spin assignments of 11 2 − , 11 2 − , 9 2 + , 11 2 + and 9 2 + to the 1982 keV, 1890 keV, 1420 keV, 1089 keV and 1067 keV levels, respectively. The determined E2/M1 mixing ratios are : δ (470) = 0.010±0.027, δ (1067) = −0.86±0.18, and δ (916) = −0.02±0.01.

Spins of the 1628-, 2441-, and 2755-keV levels inMo96determined from gamma-gamma directional and polarization directional correlations

$\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ directional correlation and polarization directional correlation experiments were performed on three cascades in $^{96}\mathrm{Mo}$ populated from $^{96}\mathrm{Tc}$ (4.3 day). Ge(Li) detectors were used in both spectrometers. Combination of the results give unique spin-${4}^{+}$ assignment to the 1628-keV level and spin-${6}^{+}$ assignments to both the 2441- and 2755-keV levels in $^{96}\mathrm{Mo}$.

Spins of the levels and multipole mixing ratios of the transitions in 95Mo

Directional correlations and polarization-directional correlations have been measured for several γ-γ cascades in 95Mo populated from the decay of 95Tc. Two Ge(Li) detectors were used in the polarization measurements and NaI(Tl)-Ge(Li) detectors were used in the directional correlation measurement. Combination of the results of these measurements give unique spin assignments of 1 2 +, 3 2 +, and 1 2 + for the 786, 821, and 1039 keV levels, respectively. The determined E2/M1 mixing ratios are: −19 ≦ δ (219) ≦ −0.6, δ (582) = +0.27 +0.05 −0.04, δ(616) = −(2.0 ± 0.2) and δ(835) = +0.04 ± 0.02.

The Jπ = 5 − level in 34S at 5.689 MeV

A polarization-direction correlation measurement at two angles, θ γ = 60° and 90°, has resulted in an unambiguious spin assignment of J π , 5 − for the 5.69 MeV level of 34S.

Analysis ofγ−γCascades by Polarization and Directional Correlation: Decay ofRh101g

A procedure is given for using the results of polarization-direction correlation and directional-correlation measurements to analyze $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ cascades in cases in which both transitions may be of mixed multipole order. A method is also presented for obtaining polarization-direction correlation coefficients from the measured rates via a Monte Carlo program based on Compton-scattering theory. The methods were applied to the 198-127-keV $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ cascade in ${\mathrm{Ru}}^{101}$ populated by the decay of ${\mathrm{Rh}}^{101g}$. It was determined that the spin of the 127-keV state is $\frac{3}{2}$ and the spin of the 325-keV state is ${\mathrm{\textonehalf{}}}^{+}$. The $\frac{E2}{M1}$ mixing ratio is 0.17\ifmmode\pm\else\textpm\fi{}0.04 for the 127-keV transition and -0.12\ifmmode\pm\else\textpm\fi{}0.03 for the 198-keV one. Relative $\ensuremath{\gamma}$-ray intensities of 94, 100, and 21, respectively, were found for the 127-, 198-, and 325-keV transitions. In a triple-coincidence scintillation-counter measurement, the $K$ internal-conversion coefficient of the 127-keV transition was found to be 0.16\ifmmode\pm\else\textpm\fi{}0.02.

Decay of 5.4 d Pm 148

The spin and parity of the 1.46 MeV excited state of Sm 148 populated by the decay of 5.4 d Pm 148 have been investigated using angular correlation techniques. Both directional correlation and polarization direction correlation measurements have been made on the 910–550 keV cascade. On the basis of these measurements, it has been possible to make an assignment of 1 − for the spin and parity of the 1.46 MeV level.

The decay of Ge 77

Directional correlation and polarization-direction correlation measurements have been done on gamma rays following the decay of Ge 77. The results are found to be consistent with previous spin assignments and a spin of 7 2 can be assigned to the 1.19 MeV level. The quadrupole content of several gamma transitions is given.

Excited energy levels in Dy160

The transitions and levels of Dy160 populated by Tb160 beta decay have been investigated by the methods of sum coincidence, gamma-gamma coincidence, angular correlation and polarization-direction correlation. The results confirm the decay scheme proposed by G.T. Ewan et al., which differs in the negative parity levels from the schemes reported by other authors. The relative intensities of the gamma rays and the quadrupole admixtures of several transitions are given.

Polarization Correlation Measurements onEu154

The spins and parities of the 1400- and 1723-kev levels in ${\mathrm{Gd}}^{154}$ are discussed on the basis of the polarization-directional correlation measurements on the 1277-123 and 725-998 kev gamma-gamma cascades following the $\ensuremath{\beta}$ decay of ${\mathrm{Eu}}^{154}$. In the case of the 1277-123-kev cascade, directional correlation measurements and the polarization correlation measurements of the 1277-kev gamma ray are made with liquid and solid sources. An attenuation in the anistropy of directional correlation and in the degree of linear polarization correlation has been observed in both the sources, the attenuation in the solid source being greater. In the 725-998 kev cascade, the polarization of either of the two radiations has been measured in two separate experiments. On the basis of these measurements, the spins and parities of both the 1400- and the 1723-kev levels in ${\mathrm{Gd}}^{154}$ are assigned ${2}^{\ensuremath{-}}$. The performance of the apparatus has been checked by measuring the polarization correlations of known cascades in ${\mathrm{Ni}}^{60}$, ${\mathrm{Ti}}^{46}$, ${\mathrm{Pd}}^{106}$, and ${\mathrm{Sr}}^{88}$.

The Second Excited State of Sn120

The directional correlation and the polarization-direction correlation of the 1.03 Mev–1.17 Mev gamma-gamma cascade in Sn 120 have been measured. It is found that the spin and the parity of the second excited state of Sn 120 is 4 and even, respectively.

Angular Correlation of the Mo95 Gamma-Gamma Cascades

The directional correlation and the polarization-direction correlation of the 838 Kev–204 Kev and 584 Kev–204 Kev gamma-gamma cascades in Mo 95 have been measured. It is found that the spin of 788 Kev level is 1/2, and that of the 1042 Kev level is either 1/2 or 3/2. The branching ratio of the positron decay is also obtained as 0.4%.