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Polarimeters were developed to measure the polarization of the proton beam at RHIC in relative scale through the asymmetry measurement of the elastic proton-carbon scattering. Recoil carbon ions with kinetic energy of 400 ≤ E ≤ 900 keV were detected by silicon strip detectors installed at 90° with respect to the beam. The absolute polarization is given by normalizing against another polarimeter implemented at RHIC, namely a polarized hydrogen gas jet polarimeter. In this report, the details of polarization measurements, data analysis, and systematic uncertainties are discussed based on the data taken during √s = 200 GeV operation of Run05 at RHIC.

A precise measurement of the analyzing power A N in proton–proton elastic scattering in the region of 4-momentum transfer squared 0.001 | t | 0.032 ( GeV / c ) 2 has been performed using a polarized atomic hydrogen gas jet target and the 100 GeV/ c RHIC proton beam. The interference of the electromagnetic spin-flip amplitude with a hadronic spin-nonflip amplitude is predicted to generate a significant A N of 4–5%, peaking at − t ≃ 0.003 ( GeV / c ) 2 . This kinematic region is known as the Coulomb nuclear interference region. A possible hadronic spin-flip amplitude modifies this calculable prediction. We present the first precise result of the CNI asymmetry and shape as a function of t . Our data are well described by the CNI prediction with the electromagnetic spin-flip alone and do not support the presence of a large hadronic spin-flip amplitude.

A study to determine the optimum magnet system for a polarized atomic hydrogen jet target is described. The design uses an atomic beam source with Ne–Fe–B permanent sextupole magnets to focus the beam and high frequency hyperfine transitions to produce nuclear polarization. A simulation model was developed and a new optimization technique was applied to the model. The study resulted in a magnet system predicted to generate an intensity of 9 × 10 16 atoms / s and a record polarized jet-target thickness of 9.5 × 10 11 atoms / cm 2 . The source design was subsequently used for construction of the RHIC polarized hydrogen jet target. The design of a polarimeter to determine the atomic polarization of the jet is also described.

Interference phenomena in (polarized) hadron collisions have often led to spectacular spin effects in the final state. These effects are expressed in terms of the spin observables, like the analyzing power AN. The interference of the electromagnetic spin-flip amplitude with a hadronic spin-nonflip amplitude in the elastic scattering of hadrons generates a significant AN at very low t ( 0.001 | t | 0.01 ( GeV / c ) 2 ) . This kinematical region is referred to as the Coulomb Nuclear Interference (CNI) region. A possible hadronic spin-flip amplitude can substantially modify the magnitude and shape of AN, which otherwise is exactly calculable. First results on AN in polarized proton-proton elastic scattering in the CNI region at 100 GeV from the 2004 polarized proton run at RHIC are presented. New results on AN in the elastic scattering of polarized protons off a carbon target over a wide energy range from 4 GeV to 100 GeV from AGS and RHIC are presented, as well. These results allow us to further study the spin dependence in elastic scattering and the mechanisms that generate these effects.

Status of the H-jet polarimeter development is reviewed. The preliminary results of atomic beam intensity and density measurements are presented.

The storage cell of the internal, longitudinally polarized, atomic gas target of the HERMES experiment is presented. The polarized atoms of hydrogen or deuterium are accumulated in an open-ended thin walled storage cell through which the circulating electron or positron beam of the HERA accelerator passes. The target areal density is 10 14 atoms=cm 2 ; two orders of magnitude larger than without the cell. The construction details of the cell are described and the cell’s performance during HERMES run of 1997–2000 is discussed. r 2002 Published by Elsevier Science B.V.

The use of storage cells has become a standard technique for internal gas targets in conjunction with high energy storage rings. In case of spin-polarized hydrogen and deuterium gas targets the interaction of the injected atoms with the walls of the storage cell can lead to depolarization and recombination. Thus the number of wall collisions of the atoms in the target gas is important for modeling the processes of spin relaxation and recombination. It is shown in this article that the diffusion process of rarefied gases in long tubes or storage cells can be described with the help of the one-dimensional diffusion equation. Mathematical methods are presented that allow one to calculate collision age distributions (CAD) and their moments analytically. These methods provide a better understanding of the different aspects of diffusion than Monte Carlo calculations. Additionally it is shown that measurements of the atomic density or polarization of a gas sample taken from the center of the tube allow one to determine the possible range of the corresponding density weighted average values along the tube. The calculations are applied to the storage cell geometry of the HERMES internal polarized hydrogen and deuterium gas target.

We have measured the longitudinal analyzing power Az of the pp→ppπ0 reaction at 375 MeV bombarding energy. We find that for certain angle combinations of the outgoing particles the observed Az is as large as 0.3, demonstrating that sizeable longitudinal analyzing powers in reactions with multi-particle final states are possible. This result has implications for pp parity violation experiments above the pion threshold. The observed Az is dominated by the interference between s and p wave pions in conjunction with nucleon-nucleon P waves in the final state.

We present a measurement of the longitudinal spin asymmetry A|| in photoproduction of pairs of hadrons with high transverse momentum pT. Data were accumulated by the HERMES experiment using a 27.5 GeV polarized positron beam and a polarized hydrogen target internal to the HERA storage ring. For h^+h^- pairs with _(pT)^(h1)>1.5GeV/c and _(pT)^(h2)>1.0GeV/c, the measured asymmetry is A_(||) = -0.28±0.12(stat)±0.02(syst). This negative value is in contrast to the positive asymmetries typically measured in deep inelastic scattering from protons, and is interpreted to arise from a positive gluon polarization.

Cross section ratios for deep-inelastic scattering from 14N and 3He with respect to 2H have been measured by the HERMES experiment at DESY using a 27.5 GeV positron beam. The data cover a range in the Bjorken scaling variable x between 0.013 and 0.65, while the negative squared four-momentum transfer Q^2 varies from 0.5 to 15 GeV^2. The data are compared to measurements performed by NMC, E665, and SLAC on 4He and 12C, and are found to be different for x < 0.06 and Q^2 < 1.5 GeV^2. The observed difference is attributed to an A-dependence of the ratio R = sigma_L / sigma_T of longitudinal to transverse deep-inelastic scattering cross sections at low x and low Q^2.

We describe an experimental setup for the measurement of polarization observables in pion production near threshold. Experiments carried out with this facility use a polarized proton beam in the Indiana University Cooler storage ring, and an internal, polarized hydrogen target. The detector system measures energy, direction and velocity of multiple outgoing charged particles that are within a forward cone of about 32° opening angle. An array of scintillators also allows the detection of neutrons. In addition to the technical details of the apparatus, we describe the procedure for data acquisition, as well as some aspects of the analysis.

The PINTEX facility at the IUCF Cooler ring, dedicated to the study of spin dependence in nucleon-nucleon interactions, has been used to measure polarization observables of the reaction pp -> pp pi0 at beam energies between 325 and 400 MeV. The stored polarized proton beam had spin projections both in the longitudinal and the transverse directions with respect to the beam momentum. We report here on the measurements of the relative transverse and longitudinal spin-dependent cross sections, deltasigma_T/sigma_tot and deltasigma_L/sigma_tot, and how from these observables the initial spin singlet and triplet cross sections are obtained. Considering angular momentum states less or equal to one, the contribution of the Ps partial waves to the cross section can be extracted.

We report a measurement of the spin-dependent total cross section ratios {delta}{sigma}{sub T}/{sigma}{sub tot} and {delta}{sigma}{sub L}/{sigma}{sub tot} of the pp{yields}pp{pi}{sup 0} reaction between 325 and 400 MeV. The experiment was carried out with a polarized internal target in a storage ring. Nonvertical beam polarization was obtained by the use of solenoidal spin rotators. Near threshold, the knowledge of both spin-dependent total cross sections is sufficient to deduce the strength of certain participating partial waves, free of any model. (c) 1999 The American Physical Society.

Exclusive incoherent electroproduction of the ρ0(770) meson from 1H, 2H, 3He, and 14N targets has been studied by the HERMES experiment at squared four-momentum transfer Q^2>0.4 GeV^2 and positron energy loss ν from 9 to 20 GeV. The ratio of the 14N to 1H cross sections per nucleon, known as the nuclear transparency, was found to decrease with increasing coherence length of quark-antiquark fluctuations of the virtual photon. The data provide clear evidence of the interaction of the quark-antiquark fluctuations with the nuclear medium.

Polarized proton targets consisting of pure spin-polarized hydrogen atoms have recently been exploited as internal targets in electron and proton storage rings. A brief overview of the development of this type of target is presented, together with some typical performance figures.

An internal polarized gas target in conjunction with a beam of polarized protons stored in the IUCF Cooler storage ring has been used to measure analyzing power and spin correlation parameters between 200 MeV and 450 MeV over a wide range of angles. A consistent absolute beam and target polarization calibration was established by ramping the stored protons up and down in energy. The analyzing power Ay and the spin correlations Axx, Ayy and Axz were measured with transverse beam polarization, while determination of Azz required the development of a longitudinally polarized beam. First experiments on the spin dependence on π0-production have recently been carried out.

Spin-polarised atomic hydrogen is used as a gaseous polarised proton target in high energy and nuclear physics experiments operating with internal beams in storage rings. When such beams are intense and bunched, this type of target can be depolarised by a resonant interaction with the transient magnetic field generated by the beam bunches. This effect has been studied with the HERA positron beam in the HERMES experiment at DESY. Resonances have been observed and a simple analytic model has been used to explain their shape and position. Operating conditions for the experiment have been found where there is no significant target depolarisation due to this effect., REVTEX, 6 pages, 5 figures

A measurement of the proton spin structure function g1p(x,Q^2) in deep-inelastic scattering is presented. The data were taken with the 27.6 GeV longitudinally polarised positron beam at HERA incident on a longitudinally polarised pure hydrogen gas target internal to the storage ring. The kinematic range is 0.021, Comment: 7 pages, 3 figures, 1 table, RevTeX latex

A polarized internal atomic-hydrogen target and a stored, polarized beam are used to measure the spin-dependent total cross section {Delta}{sigma}{sub T}thinsp/{sigma}{sub tot} for {rvec p}{rvec p}{r_arrow} pp{pi}{sup 0} , as well as the polar integrals of the spin correlation coefficient combination A{sub xx}{minus}A{sub yy} , and the analyzing power A{sub y} at four bombarding energies between 325 and 400thinspthinspMeV. This experiment is made possible by the use of a cooled beam in a storage ring. The polarization observables are used to study the contribution from individual partial waves. {copyright} {ital 1998} {ital The American Physical Society }

We have measured the $\mathrm{pp}$ spin correlation coefficients ${A}_{\mathrm{xx}},$ ${A}_{\mathrm{yy}},$ ${A}_{\mathrm{xz}}$ and the analyzing power ${A}_{y}$ at 250.0, 280.0, 294.4, 310.0, 350.0, 399.1, and 448.9 MeV over the laboratory angular range $3.5\ifmmode^\circ\else\textdegree\fi{}--43.5\ifmmode^\circ\else\textdegree\fi{}$ $({\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}=7\ifmmode^\circ\else\textdegree\fi{}--90\ifmmode^\circ\else\textdegree\fi{}).$ The statistical accuracy is approximately $\ifmmode\pm\else\textpm\fi{}0.006$ for ${A}_{y}$ and $\ifmmode\pm\else\textpm\fi{}0.02$ for ${A}_{\mathrm{mn}}$ per $1\ifmmode^\circ\else\textdegree\fi{}$ angle bin, while the corresponding scale factor uncertainties are 1.3 and 2.5 %, respectively. The experiment makes use of a polarized hydrogen gas target internal to a proton storage ring (IUCF Cooler) and a circulating beam of polarized protons. The method of calibration relative to pp spin correlation coefficients and analyzing power at 197.4 MeV, the injection energy, involves up and down ramping of the energy of the polarized beam. The data are compared to recent $\mathrm{pp}$ partial waves analyses and $\mathrm{NN}$ potential models, emphasizing in particular the energy dependence in the region of the pion production threshold.

Measurements of $\mathrm{pp}$ spin correlation coefficients ${A}_{\mathrm{xx}},$ ${A}_{\mathrm{yy}},$ and ${A}_{\mathrm{xz}}$ and analyzing power ${A}_{y}$ for $\mathrm{pp}$ elastic scattering at 197.4 MeV over the laboratory angular range 3.5 \ifmmode^\circ\else\textdegree\fi{}--43.5 \ifmmode^\circ\else\textdegree\fi{} $({\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}=7\ifmmode^\circ\else\textdegree\fi{}--90\ifmmode^\circ\else\textdegree\fi{})$ have been carried out. The typical statistical accuracy per 1$\ifmmode^\circ\else\textdegree\fi{}$ angle bin is better than 0.02 for the ${A}_{\mathrm{mn}}$ and better than 0.005 for ${A}_{y}.$ Systematic errors are negligible except for an overall normalization uncertainty of 2.5% for ${A}_{\mathrm{mn}}$ and 1.3% for ${A}_{y}.$ The experiment makes use of a polarized hydrogen gas target internal to a proton storage ring (IUCF Cooler) and a circulating beam of polarized protons. The target polarization is switched in sign and direction $(x,y,z)$ every 2 s by reversing a weak guide field $(\ensuremath{\approx}0.3$ mT). Scattered and recoil protons are detected in coincidence by two sets of wire chambers, by scintillators, and by silicon-strip recoil detectors placed 5 cm from the proton beam. Analysis methods and comparison to recent $\mathrm{pp}$ partial-wave analyses and $\mathrm{NN}$ potential models are described.

The HERMES experiment is collecting data on inclusive and semi-inclusive deep inelastic scattering of polarised positrons from polarised targets of H, D, and He. These data give information on the spin structure of the nucleon. This paper describes the forward angle spectrometer built for this purpose. The spectrometer includes numerous tracking chambers (micro-strip gas chambers, drift and proportional chambers) in front of and behind a 1.3 T.m magnetic field, as well as an extensive set of detectors for particle identification (a lead-glass calorimeter, a pre-shower detector, a transition radiation detector, and a threshold Cherenkov detector). Two of the main features of the spectrometer are its good acceptance and identification of both positrons and hadrons, in particular pions. These characteristics, together with the purity of the targets, are allowing HERMES to make unique contributions to the understanding of how the spins of the quarks contribute to the spin of the nucleon., 37 pages, 32 figures, 4 tables

A review is presented of polarization experiments in proton storage rings. Efforts to investigate narrow structures in pp scattering (“dibaryon resonances”) by means of stored polarized beams are discussed. Tests of an internal polarized hydrogen gas target at the Heidelberg TSR, and demonstration of a spin filter, are summarized, followed by an overview of the experimental program with polarized beams and polarized internal H gas targets at the IUCF storage ring (“Cooler”). Reliable operation of a polarized H gas target based on the storage-cell method has permitted measurements of pp spin correlation parameters over a wide range of angles from 200 MeV to 450 MeV with small statistical and systematic errors. The characteristics of the polarized target and the methods of polarization reversal of the proton beam are discussed. Longitudinal polarization of the stored proton beam has recently been achieved.

With a storage ring synchrotron, two additional methods have become possible to establish polarization standards at arbitrary energies, making use of the ease with which the energy of the stored beam can be changed. Both methods yield the analyzing power of a reaction at one energy in relation to the known analyzing power at a different energy. One method involves ramping of the energy of a polarized beam up and down; the other requires a polarized target. The two methods have been demonstrated in an experiment with the Indiana Cooler, and their relative consistency has been established.

We have measured the time dependence of the polarization of a stored proton beam near an intrinsic depolarizing resonance. The distance to the resonance was varied by changing the vertical tune of the storage ring. The measurements are consistent with exponential decay and with a simple model for the change of the lifetime as the resonance is approached. It was originally expected that the presence of an internal target stimulates depolarization; however, we found no evidence for such an effect.

Results are reported from the HERMES experiment at HERA on a measurement of the neutron spin structure function g1n(x, Q2) in deep inelastic scattering using 27.5 GeV longitudinally polarized positrons incident on a polarized 3He internal gas target. The data cover the kinematic range 0.023

We measured ${}^{36}$Ar$(p\ensuremath{\rightarrow}{,p}_{0})$ cross sections and analyzing powers for ${E}_{p}$ between 3.22 and 5.98 MeV, and used these data to deduce spin, parity, and widths of 17 levels in ${}^{37}$K. Our results, combined with existing information on ${}^{37}$Ca ${\ensuremath{\beta}}^{+}$ decay, yield information on the distribution of Fermi and Gamow-Teller strength in this decay. A $T=1/2$ level lying 31 keV below the ${J}^{\ensuremath{\pi}}{=3/2}^{+}$, $T=3/2$ analog of the ${}^{37}$Ca ground state was found to have ${J}^{\ensuremath{\pi}}{=3/2}^{+}$. The relative proton widths of the two levels imply an isospin-mixing matrix-element of $4.84\ifmmode\pm\else\textpm\fi{}0.43$ keV. This agrees with the value ${5.93}_{\ensuremath{-}0.65}^{+0.23}$ keV extracted from the ${\ensuremath{\beta}}^{+}$-decay intensities to the two levels, plus the Gamow-Teller to Fermi strength ratio for the 5018 keV level. We decompose the Gamow-Teller strength in ${}^{37}$Ca decay into components feeding daughter levels with ${J}^{\ensuremath{\pi}}{=1/2}^{+}$, ${3/2}^{+}$, or ${5/2}^{+}$, and compare the results to theory. None of the available shell-model calculations gives a satisfactory account of the data.

Measurements of the $\mathrm{pp}$ spin correlation coefficients ${A}_{\mathrm{xx}},$ ${A}_{\mathrm{yy}},$ and ${A}_{\mathrm{xz}}$ and analyzing power ${A}_{y}$ for $\mathrm{pp}$ elastic scattering at 197.8 MeV over the angular range $4.5\ifmmode^\circ\else\textdegree\fi{}$--$17.5\ifmmode^\circ\else\textdegree\fi{}$ have been carried out. The statistical accuracy is approximately $\ifmmode\pm\else\textpm\fi{}0.01$ for ${A}_{\mathrm{mn}}$ and $\ifmmode\pm\else\textpm\fi{}0.004$ for ${A}_{y},$ while the corresponding scale factor uncertainties are 2.4% and 1.3%, respectively. The experiment makes use of a polarized hydrogen gas target internal to a proton storage ring (IUCF Cooler) and a circulating beam of polarized protons. The target polarization $(Q=0.79)$ is switched in sign and in direction $(x,y,z)$ every 2 s by reversing a weak guide field (about 0.3 mT). The forward-scattered protons are detected in two sets of wire chambers and a scintillator, while recoil protons are detected in coincidence with the forward protons by silicon strip detectors placed 5 cm from the proton beam. The background rate from scattering by the walls of the target cell is $(0.2\ifmmode\pm\else\textpm\fi{}0.2)$% of the good event rate. Analysis methods and comparisons with $\mathrm{pp}$ potential models and $\mathrm{pp}$ partial wave analyses are described.

A high-density target of polarized atomic hydrogen gas for applications in storage rings was produced by injecting atoms from an atomic beam source into a T-shaped storage cell. The influence of the internal gas target on electron-cooled beams of 27 MeV α-particles and 23 MeV protons in the Heidelberg Test Storage Ring has been studied in detail. Target polarization and target thickness were measured by means of 27 MeV α-particles. For hyperfine states 1 + 2 a target thickness of n = (0.96±0.04) × 1014H→/cm2 was achieved with the cell walls cooled to 100 K. Working with a weak magnetic holding field (≈5 G) the maximum target polarization was PT = 0.84±0.02 when state 1 and PT = 0.46±0.01 when states 1 + 2 were injected. The target polarization was found to be constant over a period of 3 months with a net charge of Q ≈ 100C passing the storage cell.

We studied parity mixing of the ${0}_{2}^{+}$,${0}_{1}^{\mathrm{\ensuremath{-}}}$; I=1 doublet in $^{14}\mathrm{N}$ (${\mathit{E}}_{\mathit{x}}$\ensuremath{\sim}8.6 MeV) to probe the isoscalar component of the parity nonconserving (PNC) nucleon-nucleon interaction. The weak matrix element connecting the ${0}^{+}$ and ${0}^{\mathrm{\ensuremath{-}}}$ levels was determined by measuring the longitudinal analyzing power (${\mathit{A}}_{\mathit{L}}$) over the narrow ${\mathit{J}}^{\mathrm{\ensuremath{\pi}}}$=${0}^{+13}$C(p\ensuremath{\rightarrow},p) resonance at ${\mathit{E}}_{\mathit{p}}$=1.16 MeV. Scattered protons were detected in two arrays of four scintillators arranged symmetrically about the beam axis at mean angles of ${\mathit{FTHET}\mathit{\ifmmode \bar{A}\else \={A}\fi{}}}_{1}$=35\ifmmode^\circ\else\textdegree\fi{} and ${\mathit{FTHET}\mathit{\ifmmode \bar{A}\else \={A}\fi{}}}_{2}$=155\ifmmode^\circ\else\textdegree\fi{}. The PNC signal was the difference in the longitudinal analyzing power observed at the two angles. Feedback loops were used to stabilize the position, angle, and spin direction of the beam on target. The observed signal was ${\mathit{A}}_{\mathit{L}}$(FTHETA${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{2}$)-${\mathit{A}}_{\mathit{L}}$(FTHETA${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{1}$) =0.9\ifmmode\pm\else\textpm\fi{}0.6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ which corresponds to a weak matrix element 〈${\mathit{H}}_{\mathrm{weak}}$〉=0.38\ifmmode\pm\else\textpm\fi{}0.28 eV.Our measured 〈${\mathit{H}}_{\mathrm{weak}}$〉 disagrees with theoretical expectations; recent shell-model calculations by Horoi et al. using the PNC NN amplitudes of Desplanques, Donoghue, and Holstein yield 〈${\mathit{H}}_{\mathrm{weak}}$〉's that lie in the range from -0.2 eV to -0.8 eV. We briefly discuss some theoretical uncertainities that arise because the structure of the $^{14}\mathrm{N}$ doublet differs in important ways from other known parity doublets. In ancillary studies of the $^{13}\mathrm{C}$(p,\ensuremath{\gamma}) reaction at ${\mathrm{\ensuremath{\theta}}}_{\ensuremath{\gamma}}$=90\ifmmode^\circ\else\textdegree\fi{}, we found that the excitation energies and widths of the ${0}^{+}$ and ${0}^{\mathrm{\ensuremath{-}}}$ levels were (${\mathit{E}}_{\mathit{x}}$=8624\ifmmode\pm\else\textpm\fi{}2 keV, \ensuremath{\Gamma}=4.0\ifmmode\pm\else\textpm\fi{}0.3 keV, and (${\mathit{E}}_{\mathit{x}}$=8802\ifmmode\pm\else\textpm\fi{}7 keV, \ensuremath{\Gamma}=440\ifmmode\pm\else\textpm\fi{}8 keV) respectively. We also determined the following partial widths: ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}}$(8624\ensuremath{\rightarrow}0)=(0.37\ifmmode\pm\else\textpm\fi{}0.05) eV , ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}}$(8624\ensuremath{\rightarrow}3948)=(1.26\ifmmode\pm\else\textpm\fi{}0.17) eV, ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}}$(8624\ensuremath{\rightarrow}5691)=(0.43\ifmmode\pm\else\textpm\fi{}0.06) eV, ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}}$(8624\ensuremath{\rightarrow}6204)=(2.03\ifmmode\pm\else\textpm\fi{}0.28) eV, and ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}}$(8802\ensuremath{\rightarrow}0)=(25.2\ifmmode\pm\else\textpm\fi{}2.0) eV. We also report new parameters for the ${\mathit{E}}_{\mathit{x}}$=8062 keV, ${\mathit{E}}_{\mathit{x}}$=9174 keV, and ${\mathit{E}}_{\mathit{x}}$=9388 keV levels.

A target of gaseous polarized hydrogen was formed by injecting polarized hydrogen atoms (produced by Stern–Gerlach spin separation) into a storage cell consisting of a cylindrical tube open at both ends. The target was placed in a storage ring to study the target characteristics (nuclear polarization, target thickness, radiation resistance). A weak transverse guide field (5 G) was applied to define the polarization direction. When atoms in a single hyperfine state were selected, the nuclear polarization of the target was measured to be 0.80±0.02. The areal density of the target under these conditions was (5.5±0.2)×1013 H/cm2, while for two spin states (applicable to experiments in high energy rings where a strong magnetic field can be applied to the target) the target thickness was found to be (8.2±0.3)×1013 H/cm2. The target polarization was unaffected by prolonged exposure of the target to beams up to 1 mA.

The potential contribution of glaciers and ice caps to sea level rise is usually calculated by comparing the estimated total ice volume with the surface area of the ocean. Part of this total ice volume, however, does not contribute to sea-level rise, because it is below the surface of the ocean or below the levels of future lakes on land. The present communication points to this so far overlooked phenomenon and provides a first order-of-magnitude estimate. It is shown that the effect is small (most likely 1 to 5 cm sea-level equivalent) but systematic, could primarily affect earlier stages of global glacier vanishing and should therefore be adequately considered. Now-available techniques of slope-related high-resolution glacier-bed modelling have the potential to provide more detailed assessments in the future.

A measurement of the analyzing power ${\mathit{A}}_{\mathit{y}}$(\ensuremath{\theta}) in neutron-deuteron (n-d) elastic scattering below the deuteron breakup threshold is described, including a detailed discussion of the experimental apparatus and the treatment of systematic errors. The data provide a precise test of Faddeev calculations of the three-nucleon system and of the nucleon-nucleon interaction models used as inputs to these calculations. ${\mathit{A}}_{\mathit{y}}$ was measured at six angles from 44.5 \ifmmode^\circ\else\textdegree\fi{} c.m. to 145.7 \ifmmode^\circ\else\textdegree\fi{} c.m. to a precision of (7--13)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$. Polarized neutrons, produced by the $^{3}\mathrm{H}$(p\ensuremath{\rightarrow},n\ensuremath{\rightarrow}${)}^{3}$He reaction, were incident upon the target, a deuterated organic scintillator. Scattered neutrons were detected in fast coincidence with the recoil deuterons in the target. A computer simulation of the experiment was used to compensate for a number of systematic errors. Particularly important were corrections for neutron multiple scattering, accidental coincidences, and finite geometry effects. The ${\mathit{A}}_{\mathit{y}}$ data have a 2.2% scale factor uncertainty associated with uncertainty in the polarization of the incident neutron beam. The incident neutron polarization was measured in a separate experiment using n${\mathrm{\ensuremath{-}}}^{4}$He scattering from a liquid helium scintillator. The neutron polarization measurement also yielded an improved value for the polarization transfer coefficient [${\mathit{K}}_{\mathit{y}}^{\mathit{y}}$(${0}^{\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}$)=0.650\ifmmode\pm\else\textpm\fi{}0.019] in the $^{3}\mathrm{H}$(p\ensuremath{\rightarrow},n\ensuremath{\rightarrow}${)}^{3}$He reaction at ${\mathit{E}}_{\mathrm{lab}}^{\mathit{p}}$=3.80 MeV. A comparison of the ${\mathit{A}}_{\mathit{y}}$ data to Faddeev calculations shows that the discrepancy in ${\mathit{A}}_{\mathit{y}}$ observed previously at higher energies continues below the breakup threshold. A comparsion of the ${\mathit{A}}_{\mathit{y}}$ data to a recent phase shift analysis of proton-deuteron (p-d) scattering indicates that observed differences between n-d and p-d analyzing powers are only partially explained by Coulomb effects.

A storage cell has been constructed for use as an internal polarized gas target in the storage ring at the Indiana University Cyclotron Facility. The storage cell has thin teflon walls which allow for detection of low energy recoil particles. We report on nuclear polarization measurements of hydrogen atoms, produced by an atomic beam source, in this storage cell. The results indicate that a target polarization in excess of 0.70 is achieved. We discuss the design and construction details of a storage cell target and the polarization results which are based on low-energy pp spin correlation measurements using the University of Wisconsin tandem accelerator.

The FILTEX/HERMES atomic beam source (ABS) for polarized hydrogen is described. Recent improvements concern mainly the optimization of the beam forming system and a new design of the sextupole magnet system. For a precise measurement (error 5%) of the output flow a calibrated compression tube was installed. The output flow of 0.81×1017 H atoms per second in two hyperfine substates was constant within 2% in a long-term measurement over 16 h. At the FILTEX test experiment, the target density in the storage cell fed by the ABS was constant within the experimental error of 4% over a period of four months.