Calibration of the polarization of a frozen spin target

432

Nuclear Instruments and Methods in Physics Research A306 (1991) 432-438 North-Holland

Calibration of the polarization of a frozen spin target R. Abegg a, M. Ahmad b,1, D. Bandyopadhyay c.2, J. Birchall c, K. Chantziantoniou c,3, C.A. Davis a, c, N .E. Davison °, P.P .J. Delheij a, P.W. Green b, L.G. Greeniaus a,b, D.C. Healey a, C. Lapointe b,4 , W.J. McDonald b, C.A. Miller a, G.A. MOSS b,5, S.A. Page °, W.D. Ramsay c, N.L. Rodriing b , G. Roy b, W.T.H. van Oers c, G.D. Wait a, J.W. Watson d and Y. Ye b,6 ° TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3 n Department of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2N5 ` Department of Physics, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2 d Department of Physics, Kent State University, Kent, OH 44242, USA

Received 13 March 1991 A recent experiment, measuring the spin correlation parameter A in neutron-proton elastic scattering to a precision of ±0.03 at several energies in the range 200 to 500 MeV, required the polarization of the proton frozen-spin target used in the experiment to be known to an accuracy of ±2Sß . The calibration of the polarization of the frozen-spin target was accomplished through an experiment interleaved with the A experiment. An unpolarized proton beam, of an intensity comparable to the intensity of the neutron beam in the A experiment, was scattered at 24 ° (lab .) from the frozen-spin target at energies of 468 and 501 MeV. From the measured left-right asymmetries and knowledge of the proton-proton analyzing powers, A Y,(24 °, 468 MeV)=0 .4087±0.0060 and Ay(24 ° , 501 MeV) =0 .4204±0.0059, the target polarizations could be deduced. The weighted average of the ratios of the target polarization deduced in the scattering experiment and obtained from nuclear magnetic resonance measurements was found to be P,(scattering)/P,(NMR)=0 .962±0 .008(stat)±0 .021(sys)±0 .014(sys) at 468 MeV and 0.950±0.005(stat)±0 .020(sys)±0 .013(sys) at 501 MeV. By dividing the target cell holding the butanol beads, as illuminated by the incident proton beam, in three parts (top, middle, and bottom), a determination of the average polarization for each of the three parts was made . A clear decrease of the polarization going from the top to the bottom of the target cell was found. 1. Introduction A recent experiment [1], measuring the spin correlation parameter A in neutron-proton elastic scattering to an absolute accuracy of +0 .03 at several energies in the range 200 to 500 MeV, required the polarization (P,) of the proton frozen-spin target (FST), used in the experiment, to be determined to an accuracy of ±2%. The value of the polarization of frozen-spin targets and Present address: Medical Physics, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA. Present address: Department of Physics, University of Toronto, Toronto, ON, Canada M5S 1A7. Present address: Halifax Infirmary Hospital, Department of Diagnostic Imaging, Halifax, NS, Canada, B3J 2H6. Present address: Saskatoon Cancer Clinic, Saskatoon, SK, Canada S7K 6Z2. Present address: British Columbia Institute of Technology, Vancouver, BC, Canada V5G 6Z2. Present address: Nuclear Physics Division, Department of Technical Physics, Beijing University, Beijing, China 100871 .

of the more conventional dynamically polarized targets is usually obtained using nuclear magnetic resonance (NMR) techniques . It has been claimed [2] that, in a measurement of the spin correlation parameter A for proton-proton scattering at 90' c.m . as a function of energy with a dynamically polarized propanediol target, one could assign an uncertainty of ±0 .02 to the NMR determinations of the polarization for individual runs and a further 2% uncertainty, applicable to all spin correlation parameter data equally, to cover possible systematic error in the absolute calibration . A weighted average over all runs for the ratio of the values of P, from NMR measurements with the values of P, from scattering measurements gave the result [2]: Pt (scattering) /P, (NMR) = 1 .002 ± 0.005 . Determining the weighted average of the polarization ratio for the FST of ref. [1], however, with a target cell of slightly different dimensions from the one used in the A experiment, gave the result [3]: P, (scattering)/P, (NMR) = 0.961 ± 0.024( ± 0.027),

0168-9002/91/$03 .50 © 1991 - Elsevier Science Publishers B.V . (North-Holland)

R . Abegg et al. / Calibration of the polarization of a frozen spin target with the error in parentheses representing the estimate of systematic error . The latter ratio showed that the NMR technique provided results that are free of systematic error at about the 4% level, which did not meet the requirements of the Ant, experiment . The ratio was determined using the spin transfer coefficient rt at 9 ° and 477 MeV for the (p, n) reaction on deuterium . Consequently, it was deduced that the Ann experiment required an independent calibration of the polarization of the FST . It is to be noted that the region of the target cell sampled by the NMR coil(s) is, in general different from the region sampled by the beam, so that a nonuniform target polarization distribution would lead to systematic error . A nonuniform target polarization distribution may be the result of attenuation of the polarizing microwave radiation traversing the target cell or of a temperature gradient over the volume of the target cell . A nuclear scattering technique, based on p-p scattering, was used to calibrate the FST polarization at the beginning and at the end of a self-contained group of A  measurements . An unpolarized proton beam of low intensity ( < 5 X 10 6 protons/s) and of a well defined energy was scattered from the FST . For p-p scattering there exist precise determinations (to ± 0 .015 or better) of the analyzing power AY at 17' and 24' (lab .) at various discrete energies up to 520 MeV [4] . Applying the energy dependence given by phase shift analyses [5], which are free of ambiguities for energies below 800 MeV, one may interpolate to any energy in the range up to 520 MeV . To suppress uncertainties, that may be introduced by the interpolation procedure, the energy for the calibration of the polarization of the FST is chosen close to an energy where a precise determination of the p-p analyzing power is available . In the present calibration experiment scattered protons at 24 ° (lab .) and recoil protons at the complementary angle were detected in coincidence using basically the same detection apparatus as used in the Ann experiment, albeit under somewhat different conditions. Vertex reconstruction allowed the target cell, as seen by the incident proton beam, to be divided in three parts (top, middle, and bottom) and thus an indication of a nonuniformity of the polarization distribution could be obtained. In section 2 a brief description is presented of the experimental arrangements and procedures, section 3 describes the data analysis, while section 4 reports the results as well as some conclusions .

2. Experiment The layout of the experiment is shown in fig . 1 . Since the experiment was executed on the TRIUMF polarized neutron bean-dine (immediately preceding and following the A ., measurements), details of the beamline, the

43 3

Unpolarized protonbeam

l,iquid hydrogen target ILH21 or Graphite target ICI

TOF startsantillalor Superconducting solenoid

1

Horizontal drill chamber OF stop scattillator olarized proton target IFSTI

Recoil proton detector

Scattered proton detector

Fig. 1 . Experimental layout used in the p-p elastic scattering experiment to calibrate the FST polarization . The diagram is not to scale. The apparatus depicted above was originally designed for the "Test of Charge Symmetry Breaking" experiment and was used in the A,,y (B) experiment as well. frozen-spin target, and the detection apparatus can be found in earlier reports [6-9]. In the following only the differences in performing the proton scattering calibration experiment and the neutron scattering experiments will be presented . To obtain a low intensity scattered proton beam (< 5 X 10 6 s -1 ) along the 9 ° (lab .) neutron beamline a 150 nA unpolarized primary proton beam was incident on the neutron production target filled with liquid hydrogen (thickness 1 .4 g/cm2 ) instead of liquid deuterium or on a target consisting of five 1 .65 mm thick graphite disks with spacings of 50 .8 mm (total thickness 1 .49 g/cm2 ) . The liquid hydrogen was contained in a stainless steel cylindrical cell 197 mm long by 50 .8 mm

434

R Abegg et al. / Calibration

of the polarization of a frozen

diameter, with walls of 0 .25 mm and end windows of 0.051 mm. When in operation the liquid hydrogen target was separated from the beamline vacuum by 0 .13 mm stainless steel windows . The primary proton beam energy was continuously monitored during the experiment using a twin detector assembly (set symmetrically about the beam axis) viewing a thin kapton foil, which was located 6 .32 m upstream of the secondary proton beam production target center . The twin detector assembly observed p-p coincident events scattered from the kapton foil at 17' (lab .) (with the recoil particles observed at the complementary angle of - 69' (lab .)) and determined the proton stopping distribution as the average of the left and right distributions . The sensitivity to changes in the beam energy was ± 35 keV at 500 MeV. The absolute value of the beam energy could be deduced from cross calibrations of the range counter assemblies with n-p - d-m° threshold measurements [10] . The incident proton beam had energies of 497 and 512 MeV, respectively, with an absolute uncertainty of f 1 MeV. This corresponded to secondary proton beams of 468 and 501 MeV, respectively, at the FST center . Relative changes in the beam energy corresponded to distributions with a a of +_ 0 .7 MeV for the calibration with a primary LH 2 target and with a a of ±0 .1 MeV for the calibration with a primary carbon target . The first is mainly due to an electronics problem with one of the twin detector assemblies. Combined with the uncertainty in the incident proton beam energy and the uncertainty of ±5% in the energy loss determination, the uncertainty in the secondary proton beam energy at the FST center amounts to ± 2 and ± 1 MeV, respectively, for the calibrations with LH 2 and carbon primary targets . These energy uncertainties contributed uncertainties to the calibration of the FST polarization of ±0 .~% and ±0 .1%, respectively. The secondary proton beam passed through a 3 .37 m long steel collimator with an aperture which varied from 39 .1 mm wide x 18 .6 mm high upstream to 46 .1 mm wide x 32 .2 mm high downstream. The distance between the center of the LH 2 (or C) target and the entrance and exit of the collimator was 2 .92 m and 6 .29 m, respectively . The unwanted normal component of polarization resulting from scattering in the LH 2 or graphite was rotated into the horizontal scattering plane using a superconducting solenoid placed along the beamline immediately downstream of the collimator . Due to parity conservation any component of polarization of the incident beam in the scattering plane will not contribute to a left-right asymmetry provided that the FST polarization direction is perpendicular to the scattering plane . The superconducting solenoid was run with both polarities to cause a 90' rotation clockwise or counterclockwise, respectively . The magnetic field in the two dipole magnets was set

spin target

to values up to 10 mT as required to correct for the deflection of the proton beam caused by a slight misalignment of the superconducting solenoid and by the cyclotron magnet fringe field . The incident proton beam profile at the FST, at 12 .85 m from the center of the LH 2 or graphite targets, was determned using a 0.08 x 0 .08 m2 drift chamber placed 0 .67 m upstream of the FST center. Since the vertical dimension of the beam at the FST (due to the focussing effect of the superconducting solenoid) was smaller than the vertical dimension of the target cell (50 mm high), the second dipole magnet was also used as a vertical steering magnet to illuminate the full height of the target cell in three consecutive steps. Software cuts on the incident beam images at the FST center removed typically 17% and 9% of the events projected on the x (transverse horizontally) and y (transverse vertically) coordinate axes, respectively. A time-of-flight system based on two 0.8 mm thick scintillators placed upstream of the FST with a separation as large as possible (6 .005 m) was used to isolate the protons of interest . Since the resolution of this time-of-flight system was 0 .5 ns (FWHM), only a loose cut on the incident proton momenta could be made . Butanol beads with an approximate diameter of 1 .5 mm were contained in a 20 mm wide x 35 mm thick x 50 mm high target cell . During data collection the target cell was maintained at a mixing chamber temperature of 45 ± 5 mK in a magnetic holding field of 0 .257 T . This ensured average polarization decay times (approximately 800 h) well in excess of the data-taking periods (approximately 24 h) . The holding field at the FST center was pointing vertically up (deviation from the vertical direction was less than I') . X-ray radiographs of the FST to determine the position of the target cell relative to the cryostat shell were taken before and after the data-taking periods . The calibration measurements were made for one direction of the holding field with two directions of the target polarization . The scattered protons from the FST were detected using two detector assemblies mounted on booms symmetrically placed at 24' to the incident beam direction . The angles were corrected for the deflection of the protons incident on the FST due to the field about the FST (a typical deflection of 0 .65') and for the deflection of both the scattered and recoil protons in the same holding field . Typical corrections for scattered and recoil proton angles were 1 .50' and 2 .30', respectively . The effects of the uncertainties in these corrections were small compared to the effect on APt/P, of the ±0 .05 ° uncertainty in the proton detector angle setting . The detector elements on the booms were the same as used in the A  experiment [1] . The recoil protons were detected in coincidence in two detector arms each consisting of the central scintillator "veto" panel (368 mm wide x 6 .4 mm thick), placed at 2.725 m from the FST

R. Abegg et al / Calibration

of the polarization of a frozen

center, of each neutron detector array and a 0 .58 X 0 .58 m2 delay line chamber (DLC) mounted on a rail in front of the array at a distance of 2 .402 m from the FST center . The neutron array-DLC combinations were placed about 61 ° on both sides of the incident beam direction after correcting for the deflection of the recoil protons due to the magnetic field about the FST . A scintillator with a 0 .10 m wide X 0 .18 m high aperture was installed on each recoil arm 0 .50 m away from the FST center to define events originating in the target cell .

3. Data analysis 1111 A detected scattered proton required coincident signals from the proton time-of-flight start counter, the DE counter, and the E counter, whereas a detected recoil proton required coincident signals from the proton time-of-flight start counter and from the central panel of the neutron detector array . There was no on-line rejection of data . In addition to scattering events, as defined by the coincidence trigger, including incident particle time-of-flight information, scaler data corresponding to the primary and secondary beam monitors (polarimeters and beam energy monitors), and corresponding to the status of the FST and magnetic holding field were recorded concurrently . Track reconstruction of the scattered protons followed from the two pairs of DLCs placed on the booms . The DLCs were positioned at average distances of 0 .612 m, 1 .670 m, 2 .830 m and 2.996 m from the FST center . Typical coordinate resolutions in x and y were ± 1 .4 and +0 .8 mm at half maximum, respectively, which should be compared with intrinsic resolutions of ±1 .0 mm and ±0 .7 mm, corresponding to the cathode strips running parallel or perpendicular to the anode wire planes . The mean multiple scattering angle amounted to 0.6' at 24' (lab .) (nominal scattering proton angle) and to 1 .1 ° at 61 ° (lab .) (nominal recoil proton angle) . The image of the FST was constructed from both left and right events separately by projecting onto the y-z plane. The time-of-flight of the scattered protons followed from the signals of the start and stop scintillators on the booms, placed at distances of 0 .410 m and 3 .444 m from the FST center . The start scintillators were viewed by two photomultipliers (one at the top and one at the bottom of the scintillator) via lightguides . Since the start scintillators (0 .8 mm thick) had dimensions of 175 X 175 mm2 (width X height), no position dependent corrections were applied . The stop scintillators (6 .4 mm thick) had dimensions of 0 .67 m wide X 0 .69 m high and were viewed via lightguides by four photomultipliers (two at the top and two at the bottom of the scintillator) . For position dependent timing corrections, the

spin target

43 5

scintillator was represented by a matrix of 28 rows and 18 columns. The average transit times to the four photomultiplier tubes had been determined in a previous experiment [9] . The time-of-flight of the recoil protons followed from the signals of the scattered proton start scintillator and the central " veto" scintillator panel. The latter was viewed via lightguides by two photomultipliers (one at the top and one at the bottom) . All timing information was obtained by software averaging of the respective photomultiplier signals . The scattered and recoil proton energies were reduced from the flight times and the path lengths . The energies were compared with those calculated from kinematics . Typical difference spectra have standard deviations of 48 MeV for scattered protons and 13 MeV for recoil protons. The widths of the difference spectra result from timing resolutions of the various scintillator detectors, energy spread of the incident proton beam, and multiple scattering . From conservation of energy and momentum, four independent constraints can be applied to the data : i) the sum of the kinetic energies of the scattered and recoil protons should be equal to the kinetic energy of the incident proton, ii) the opening angle between the scattered and recoil protons should be equal to the one calculated from kinematics, iii) the planes formed by the directions of incident proton and scattered proton and of incident proton and recoil proton should coincide or the non-coplanarity angle should be equal to zero, and iv) the net transverse momentum should be equal to zero . The four distributions so formed for each data run had typical standard deviations of 50 MeV, 1 .25 ° , 1 .6 ° , and 34 MeV/c, respectively . The p-p elastic scattering events were selected from the events that had passed the software cuts on the data representations by imposing a further X2 condition defined as 4

Xsum - Y- X? < S . =t

Here the index t corresponds to the four kinematical relations defined above, and s equals 10 .0, 15 .0, or 20 .0 . The final results did not depend in a statistically significant way on the choice of s . The data were expressed as : L t = n±Nl2 L e~ao (8~~1±Pt Ay (B )] , where the superscripts correspond to the two polarization states of the target, n is the number of incident protons, N is the number of free target protons/cm2 , 2 is the solid angle, and ao is the unpolarized differential cross section . Similar expressions can be formed for right-scattered events . The overall detector efficiencies were about constant from run to run and differed only

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R. Abegg et al. / Calibration of the polarization of a frozen spin target

slightly for left-scattered and right-scattered events (range of values for E is 0 .92 to 0 .95) . The data were corrected for background in a manner analogous to the A  experiment [1] . The background subtraction contributes an uncertainty of ±0 .5`90 to the determination of the target polarization . The target polarization follows from the expression p =

E (A

p)

with

and r= (

(P, (scattering)) =

L+R _

L R

i/2 .

+

P, (scattering) = IL P, (NMR),

)

4 . Discussion The average analyzing powers over the 8 ° overlap region of the two scattering detectors was calculated from the expression :

f

A P (B)w(B) dB

f

w(B) dB

where the weighting function was determined from data taken with the target in the unpolarized state . The central p-p analyzing power values used in the calibration are A P (24 ° , 468 MeV) = 0 .4087 ± 0 .0060 and A P (24 ° , 501 MeV) = 0 .4204 ± 0.0059 . The analyzing power values were taken from the energy dependent solution SP88 of Arndt et al . [5] with errors estimated on the basis of the differences between the solution SP88 of Arndt et al ., the single-energy solutions C450 and C500 (based on the same data selection), and the solution S500 of Bystricky et al. [12] . The single-energy

Table 1 Polanzations (P, (scattering)) and calibration constants (h) FST bin Middle Bottom

a

(EP)l(AP)

is related to the value obtained from the NMR measurements by the following expression :

Here (A p ) is the average analyzing power over the angular acceptance of the scattering detectors . Use of the ratio r cancels many systematic errors as can be seen by substituting the expressions for L+, R -, L-, and R + .

Top

phase shift solutions C450 and C500 of Arndt et al . and S500 of Bystricky et al . use restricted databases around the nominal energies of 450 and 500 MeV, respectively. The angular and energy dependence about the central values was taken from the energy dependent solution SP88 of Arndt et al . Note that the precise experimental determinations of the p-p analyzing powers [4] carry great weight in the phase shift analyses . The target polarization obtained from the p-p scattering asymmetries :

P,(468 MeV) 0.808 t 0.015 0.768 ±0.010 0 .734±0.015

where p is the calibration constant . In order to obtain the FST polarization distribution, the FST cell was segmented in three bins of equal size (top, middle, and bottom) . With a six bin segmentation (by bisecting the three horizontal bins by a vertical cut), the left-right difference in the FST polarizations for the top, middle, and bottom bins was 0 .03, 0 .02, and 0 .04, respectively, smaller than the total error on the value of the polarization for the entire horizontal bins . The average polarizations and the deduced calibration constants j, for the three horizontal bins are shown in table 1. It is evident from the values quoted in table 1, that the FST polarization decreased from the top to the bottom of the sample cell . If one assumes that the initial polarization distribution was uniform, the observed differences in the average polarizations going from the top to the bottom of the sample cell could be caused by varying decay constants as a result of differences in temperature and magnetic holding field . The temperature differences required to give the observed polarization distributions are 19 and 10 mK for the 468 and 501 MeV results, respectively. With only one mixing chamber thermometer located at the bottom of the FST sample cell, it was not possible to verify this conjecture. The measured level of homogeneity of the magnetic holding field precluded the second cause for the difference in average polarizations . A second possibility for the observed differences in the average polarizations

a

P,(501 MeV)

W(468 MeV)

p(501 MeV)

0.792 +0 .008 0.762±0 .006 0.763±0 .008

1 .009 ± 0.019 0.961+0 .012 0.922±0 .019

0.971 +0 .010 0.935+0 .007 0.937±0 .010

The quoted errors are purely statistical ; the results are for below .

X2

< 10 . The common systematic errors and scale errors are discussed

R . Abegg et al. / Calibration of the polarization of a frozen spin target

is an initial nonuniform polarization distribution due to attenuation of the microwave radiation traversing the FST sample cell . Clearly, no distinction between temperature differences and microwave attenuation can be made based upon the parameters that were measured . A nonuniform polarization distribution has earlier been observed for various targets under various conditions . For instance, from measurements with a partly filled target space, deviations of 1 part in 35 were derived in ref. [131 . Sampling the target cell with two [14] or eight [15] NMR coils showed variations of a few percent. The calibration constants Faded~eed have values near unity at the top of the target cell but deviate from unity at the middle where the NMR coil was located. The average calibration constant p over the entire target cell was found to be equal to 0.962 ± 0.008(stat) ± 0.021(syst) ± 0.014(syst) at 468 MeV (with the LH z target) and 0.950 ± 0.005(stat) ± 0.020(syst) ± 0.013 (syst) at 501 MeV (with the graphite target). The first systematic error is due to the error in the primary proton beam energy, misalignment of the apparatus, background subtraction uncertainties, the presence of various extraneous beam and FST polarization components, and the error in the NMR values . For the two major data taking runs respectively three and four thermal equilibrium calibrations of the NMR sensitivity were measured at a temperature of approximately 1.6 K. The average of the two variances for these distributions was 2% . The error in the NMR enhancement factor was ten times smaller and has been neglected. Therefore, an error of 2% was assigned to the NMR polarization values . Contributions to the first systematic error due to uncertainties in the corrections for the holding field deflections and the spin precession in the superconducting solenoid were negligibly small. The various contributions to the first systematic error are listed in table 2 . The second systematic error is a scale error and is due to the uncertainty in the p-p analyzing power AP and determined from the phase shift analyses . The weighted average for the two values of tt is 0.953 ± 0.004(stat) ± 0.020(syst) ± 0.014(syst) ; this corresponds to an absolute error of ±2 .6% of the value of Ft . The above result compares well with the similar relation between the target polarization obtained using n-p scattering results and the target polarization obtained using NMR measurements, extracted in the previous charge symmetry breaking experiment [9]. The factor la for that experiment was found to be equal to 0.961 ± 0.024(±0.027) [31, where the error in parentheses is a scale error due to the error in the neutron beam polarization as deduced from phase shift analyses (the latter reflects mainly the uncertainty in the polarization transfer coefficient rt ) and the first error is mainly due to reproducibility uncertainties in the NMR measurements. In conclusion, the determination of the polarization

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Table 2 Systematic error contributions Contributing effects

Uncertainty m primary proton beam energy Misalignment of the detector system Uncertainty in the corrections of the holding field deflections Reproducibility uncertainty of the NMR values Uncertainty m background subtraction Presence of extraneous beam and FST polarization components Total systematic error

Additional scale error due to the uncertainty in the p-p analyzing power

468 MeV

AP/P

501 MeV (LH Z target) (graphite target) 00021

0 .0011

0.0022

0.0022

0.0002

0.0002

0.0200

0.0200

0.0049

0.0047

0.0056

0.0028

0.0216

0.0209

0 .0147

0.0140

calibration constant Ft with an absolute accuracy of ±2.6% of its value permitted the Ann spin correlation measurements to be made with uncertainties of +_ 0.03 or better . Acknowledgement Work supported in part by the Natural Sciences and Engineering Research Council of Canada . References D. Baridyopadhyay, R. Abegg, M. Ahinad, J. Birchall, K Chantziantoniou, C.A. Davis, N.E . Davison, P.P .J . Delheij, P.W . Green, L.G. Gieemaus, D.C . Healey, C. Lapointe, W.J . McDonald, C.A . Miller, G.A . Moss, S.A . Page, W.D . Ramsay, N.L . Rodriing, G. Roy, W.T.H. van Oers, G.D . Wait, J.W . Watson and Y. Ye, Phys . Rev C40

(1989) 2684 . [2] M.W . McNaughton, H.W . Baer, P.R . Bevington, F.H .

Cverna, H.B . Willard, E. Winkelmann, E.P . Chamberlin, J.J . Jaimer, N.S.P . King, J.E. Simmons, M.A . Schaidt and H. Willines, Phys . Rev. C23 (1981) 838 . R. Abegg, D. Baridyopadhyay, J. Biichall, E.W . Cairns, G.H Coombes, C.A. Davis, N.E . Davison, P.P .J. Delheij, P W. Green, L.G . Gieeniaus, H.P . Gublei, D.C. Healey, C. Lapointe, W.P . Lee, W.J . McDonald, C.A. Miller, G.A . Moss, G.R . Plattner, P.R. Pofferiberger, W.D . Ramsay, G.

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Roy, J. Soukup, J.P . Svenne, R.R. Tkachuk, W.T .H . van Oers, G.D . Wait and Y.P . Zhang, Nucl . Instr. and Meth . A254 (1987) 469. [41 L.G . Greemaus, D.A . Hutcheon, C.A . Miller, G.A . Moss, G. Roy, R. Dubois, C. Amsler, B.K .S . Koene and B.T . Murdoch, Nucl . Phys . A322 (1979) 308. R.A Arndt and D.L . Roper, SAID, Scattering Analyses Interactive Dial-In program, Virginia Polytechnic Institute and State University Report (1980), unpublished, solution SP88 ; and R.A . Arndt, J.S . Hyslop III and L.D . Roper, Phys . Rev. D35 (1987) 128. [6] R. Abegg, J. Birchall, E.W . Cairns, G.H . Coombes, C.A . Davis, N.E . Davison, P.W . Green, L.G . Greemaus, H.P . Gubler, W.P . Lee, W.J . McDonald, C.A . Miller, G.A . Moss, G.R . Plattner, P.R. Poffenberger, G. Roy, J.P . Soukup, J.P . Svenne, R.R . Tkachuk, W.T .H . van Oers and Y.P . Zhang, Nucl . Instr. and Meth . A234 (1985) 11 . [71 Ibid ., p. 20. [8] P.P .J . Delheij, D.C . Healey and G.D . Wait, Nucl . Instr. and Meth . A264 (1988) 186. R. Abegg, D. Bandyopadhyay, J. Birchall, E.W . Cairns, G.H. Coombes, C.A. Davis, N.E . Davison, P.P.J . Delheij, P.W . Green, L .G . Greeniaus, H.P . Gubler, D.C . Healey, C. Lapointe, W.P . Lee, W.J. McDonald, C.A . Miller, G.A .

[10]

[11] [12]

[131

[14]

[15]

Moss, G.R . Plattner, R.P . Poffenberger, W.D. Ramsay, G. Roy, J. Soukup, J.P. Svenne, R.R . Tkachuk, W.T .H . van Oers, G.D . Wait and Y.P. Zhang, Phys . Rev. D39 (1989) 2464 . D.A . Hutcheon, E. Korkmaz, G.A . Moss, R. Abegg, N.E. Davison, G.W.R. Edwards, L.G . Greemaus, D. Mack, C.A . Miller, W.C . Olsen, I.J . van Heerden and Y Ye, Phys . Rev. Lett . 64 (1990) 176. For full details see : K. Chantziantomou, M.Sc. thesis, University of Manitoba (1989) unpublished . The Bystricky et al . or Saclay-Geneva solution S500 was also obtained from SAID, Scattering Analyses Interactive Dial-In program [5]. P.S . Booth, L.J . Carroll, G.R . Court, P.R . Damel, R. Gamet, C.J. Hardwick, P .J . Hayman, J.R. Holt, A.P Hufton, J.N . Jackson, J.H . Norem and W.H . Range, Nucl . Phys . B121 (1977) 45 . P.R . Cameron, D.G . Crabb and S.L . Lim, in : High Energy Spin Physics - 1982, AIP Conf. Proc . No. 95 (1983) P_ 488. S.C . Brown, G.R. Court, R. Garnet, O. Hartmann, T. Niinikoski, J.M . Rieubland and A Ryllart, Proc . 4th Int. Workshop on Polarized Target Materials and Techniques, Bad Honnef, 1984, p. 102.