- Email: [email protected]
Improved quality of some sources of linearly polarized photons
NUCLEAR 1N57RUMEN75
AND M E 7 H 0 D 5
113
(1973) 149-150;
•
N0R7H-H0LLAND
Pu8L15H1N6
c0.
1MPR0VED QUAL17Y 0 F 5 0 M E 5 0 U R C E 5 0 F L1NEARLY P0LAR12ED P H 0 7 0 N 5 W. R. D1X0N and R. 5. 5 7 0 R E Y
D1v1510n 0f Phy51c5, Nat10na1 Re5earch C0unc11, 0ttawa, Canada A. LJU81~1(~*, R. 7. J 0 N E 5 and 8. A. L 0 6 A N
Un1ver51ty 0f 0ttawa-Car1et0n Un1ver51ty Nuc1ear Phy51c5 6r0up, Phy51c5 Department, Un1ver51ty 0f 0ttawa, 0ttawa 2, Canada Rece1ved 13 Apr11 1973 7he 4ua11t1e5 0f the react10n5 24M9(p, p~)24M9 and 5 6 F e (p, p~)58Fe, when u5ed a5 50urce5 0f 11near1y p01ar12ed ph0t0n5,
have 6een 1nve5t19ated. 7he advanta9e 0f pr0t0n5 0f ener91e5 h19her than th05e c0mm0n1y u5ed 15 p01nted 0ut.
1nten5e 6eam5 0f 11near1y p01ar12ed ph0t0n5 are 0ften pr0duced 1n (p,p•y) react10n5. 7hey can 6e u5ed t0 ca116rate y-ray p01ar1meter5 and they a150 have app11cat10n5 1n at0m1c phy51c5. 7he 2.01 MeV and the 2.40 MeV re50nance5 1n the react10n 24M9(p, p~)24M9 have 0ften 6een u5ed a5 50urce5 0f 11near1y p01ar12ed 1.37 MeV ph0t0n51-5). 7he 56Fe(p,p•y)56Fe react10n, at a pr0t0n ener9y 0f 3.43 MeV, ha5 a150 6een u5ed t0 pr0duce 11near1y p01ar12ed 0.847 MeV ph0t0n51• 4). 7he t1me nece55ary t0 ca116rate a p01ar1meter, 0r t0 mea5ure an a5ymmetry a550c1ated w1th a phy51ca1 pr0ce55 wh1ch 15 5en51t1ve t0 11near p01ar12at10n, t0 a 91ven re1at1ve 5tat15t1ca1 accuracy, 15 1nver5e1y pr0p0rt10na16) t0 1P 1, where 1 15 the 1nten51ty 0f the ph0t0n 6eam and P 15 the de9ree 0f 11near p01ar12at10n (P•< 1). 7h15 5u99e5t5 the u5e 0f 1P 2 a5 a f19ure 0f mer1t f0r the 4ua11ty 0f the ph0t0n 6eam. 1t 15 the purp05e 0f th15 n0te t0 5h0w that, 0n the 6a515 0f th15 f19ure 0f mer1t, 1t 15 advanta9e0u5 t0 u5e h19her ener9y pr0t0n5 and th1ck tar9et5 when the react10n5 24M9(p,p• y)24M9 and 56Fe(p, p• y)56Fe are u5ed a5 50urce5 0f 11near1y p01ar12ed ph0t0n5. 1f the an9u1ar d15tr16ut10n W(0) 0f the y-ray5 15 expre55ed a5
An9u1ar d15tr16ut10n5 and y1e1d5 were mea5ured f0r the react10n5 24M9(p,p•y)24M9 and 56Fe(p,p~y)56Fe u51n9 the pr0t0n 6eam 0f the 4 MV Van de 6 r a a f f acce1erat0r 0f the Nat10na1 Re5earch C0unc11 0f Canada. 7he th1ckne55e5 0f 60th the ma9ne51um and the 1r0n tar9et were 9reater than the ran9e 0f the pr0t0n5. 7he an9u1ar d15tr16ut10n 0f the 1.37 MeV y-ray5 fr0m the react10n 24M9(p,p~y)24M9 wa5 meared at a pr0t0n ener9y 0f 3.07 MeV. An9u1ar d15tr16ut10n5 0f the 0.847 MeV y-ray5 pr0duced 1n the react10n 56Fe(p, p• y)56Fe were mea5ured at pr0t0n ener91e5 0f 3.43 MeV and 3.92 MeV. 7he re1at1ve 1nten51ty 0f the5e y-ray5 em1tted at 90 ° t0 the pr0t0n 6eam d1rect10n wa5 mea5ured 1n the pr0t0n ener9y ran9e 0f 1.95 MeV t0 3.10 MeV f0r the react10n 24M9(p, p• y)24M9 and the pr0t0n ener9y ran9e 0f 2.8 MeV t0 4.0 MeV f0r the react10n 56Fe(p, p•y)56Fe. 7he re5u1t5 are ta6u1ated 1n ta61e 1. 7he m0va61e 6e(L1) c0unter u5ed t0 mea5ure W(0) wa5 5uff1c1ent1y d15tant fr0m the tar9et that c0rrect10n5 f0r the f1n1te 512e 0f the detect0r were ne9119161e ( < 1 % ) . A 5ma11 c0rrect10n wa5 made f0r a650rpt10n 0f the em1tted y-ray5 1n the tar9et 6ack1n9. 7he data f0r the 2.01 MeV and the 2.40 MeV re50nance5 1n 24M9(p,p•y)24M9 are taken fr0m pu6115hed re5u1t54). 7he mea5urement 0f W(0) f0r the react10n 56Fe(p,p•y)56Fe at a pr0t0n ener9y 0f 3.43 MeV 15 1n exce11ent a9reement w1th a prev10u5 re5u1t4). 7he re1at1ve y1e1d5 1 (90 °) are n0rma112ed t0 the 2.01 MeV re50nance f0r the 24M9(p, p•y)24M9 react10n and t0 the y1e1d at 3.43 MeV f0r the 56Fe(p, p• y)56Fe react10n. F19ure5 0f mer1t 1P 2 are 91ven 1n the 1a5t c01umn 0f ta61e 1, w1th e5t1mated accurac1e5 0f 10-20%. 0 n the 6a515 0f the def1ned f19ure 0f mer1t the 4ua11ty 0fthe ph0t0n 6eam pr0duced 6y 3.07 MeV pr0t0n5 and a th1ck ma9ne51um tar9et 15, f0r a 91ven pr0t0n 6eam
W ( 0 ) = 1 + a 2 P2 (0) + a 4 P4 (0),
where P2 (0) and P4(0) are Le9endre p01yn0m1a15, then the 11near p01ar12at10n 0f E2 ph0t0n5 em1tted at 90 ° t0 the pr0t0n 6eam d1rect10n 15 91ven 6y 7) P(90 °) =
1.5 a2 +0.625 a 4
1--0.5 a2 +0.375 a 4" 7hu5, P (90 °) can 6e der1ved fr0m a mea5urement 0f W(0). * 0 n 1eave fr0m: 1n5t1tute ••Rudjer 80~k0v16~, 2a9re6, Yu9051av1a.
149
150
W . R . D1X0N et a1. 7A8LE 1
Character15t1c5 0f ph0t0n 6eam5 pr0duced 6y pr0t0n 60m6ardment 0f th1ck tar9et5 0f M9 and Fe. 7he re1at1ve 1nten51t1e5 1 (90°) and f19ure5 0f mer1t 1p2 are n0rma112ed 5eparate1y f0r each tar9et. Pr0t0n ener9y Ph0t0n ener9y (MeV) (MeV) 2.01 2.40 3.07 3.43 3.92
1.37 1.37 1.37 0.847 0.847
7ar9et
a2
a4
P (90°)
1 (90°)
1P 2
M9 M9 M9 Fe Fe
0.45 0.55 0.33 0.36 0.32
0 - 0.52 0.28 -- 0.23 -- 0.21
0.87 4.0.05 0.94 • 0.08 0.71 4.0.03 0.54 4-0.02 0.45 4. 0.02
1.0 4.0 50 1.0 3.3
0.8 3.5 25 0.29 0.67
CUrrent, appr0X1mate1y 7 t1me5 6etter t h a n the p h 0 t 0 n 6 e a m pr0dUCed at the 2.40 MeV re50nance, a n d appr0X1mate1y 30 t1me5 6etter t h a n the p h 0 t 0 n 6eam pr0dUCed at the 2.01 MeV re50nance. F 0 r the 56Fe(p,p•7)56Fe react10n the 4ua11ty 0f the p h 0 t 0 n 6eam p r 0 d u c e d w1th 3.92 MeV pr0t0n5 15 appr0x1mate1y 2.3 t1me5 6etter t h a n the 6 e a m pr0duced 6y 3.43 MeV pr0t0n5. 7he5e 1mpr0vement5 1n the 4ua11ty 0f the p h 0 t 0 n 6eam5 are part1cu1ar1y 1mp0rtant when 5y5tem5 w1th 10w detect10n eff1c1enc1e5 are 6e1n9 1nve5t19ated a n d they have 6een u5ed advanta9e0u51y 1n 1nve5t19at10n5 0f pr0ce55e5 1n at0m1c phy51c5 w1th 11near1y p01ar12ed ph0t0n58). 7 h e auth0r5 W15h t0 t h a n k M r J. D. 5t1n50n f0r prepar1n9 the tar9et5. 0 n e 0f U5 (8.A.L.) W0U1d a150 11ke t0 t h a n k the Nat10na1 Re5earCh C0UnC11 0f C a n a d a
a n d the At0m1C Ener9y C0ntr01 8 0 a r d 0f C a n a d a f0r f1nanC1a1 a5515tance.
Reference5 1) 6. J. Mcca11um, Phy5. Rev. 123 (1961) 568. 2) 6. 7. Ewan, 6. 1. Ander550n, 6. A. 8arth010mew and A. E. L1ther1and, Phy5. Letter5 298 (1969) 352. 3) 6. E. 0wen and Y. K. Lee, Nuc1. 1n5tr. and Meth. 82 (1970) 173. 4) A. E. L1ther1and, 6. 7. Ewan and 5. 7. Lam, Can. J. Phy5. 48 (1970) 2320. 5) A. Lju61~16 and 8. A. L09an, Nuc1. 1n5tr. and Meth. 99 (1972) 269. 6) 8. A. L09an, R. 7. J0ne5 and A. Lju61(;16, Nuc1. 1n5tr. and Meth., t0 6e pu6115hed. 7) L. W. Fa99 and 5. 5. Hanna, Rev. M0d. Phy5.31 (1959) 711. 8) R. 7. J0ne5, 8. A. L09an, A. Lju61616, W. R. D1x0n and R. 5. 5t0rey, 8u11. Am. Phy5. 50c. 18 (1973) 142.
AND M E 7 H 0 D 5
113
(1973) 149-150;
•
N0R7H-H0LLAND
Pu8L15H1N6
c0.
1MPR0VED QUAL17Y 0 F 5 0 M E 5 0 U R C E 5 0 F L1NEARLY P0LAR12ED P H 0 7 0 N 5 W. R. D1X0N and R. 5. 5 7 0 R E Y
D1v1510n 0f Phy51c5, Nat10na1 Re5earch C0unc11, 0ttawa, Canada A. LJU81~1(~*, R. 7. J 0 N E 5 and 8. A. L 0 6 A N
Un1ver51ty 0f 0ttawa-Car1et0n Un1ver51ty Nuc1ear Phy51c5 6r0up, Phy51c5 Department, Un1ver51ty 0f 0ttawa, 0ttawa 2, Canada Rece1ved 13 Apr11 1973 7he 4ua11t1e5 0f the react10n5 24M9(p, p~)24M9 and 5 6 F e (p, p~)58Fe, when u5ed a5 50urce5 0f 11near1y p01ar12ed ph0t0n5,
have 6een 1nve5t19ated. 7he advanta9e 0f pr0t0n5 0f ener91e5 h19her than th05e c0mm0n1y u5ed 15 p01nted 0ut.
1nten5e 6eam5 0f 11near1y p01ar12ed ph0t0n5 are 0ften pr0duced 1n (p,p•y) react10n5. 7hey can 6e u5ed t0 ca116rate y-ray p01ar1meter5 and they a150 have app11cat10n5 1n at0m1c phy51c5. 7he 2.01 MeV and the 2.40 MeV re50nance5 1n the react10n 24M9(p, p~)24M9 have 0ften 6een u5ed a5 50urce5 0f 11near1y p01ar12ed 1.37 MeV ph0t0n51-5). 7he 56Fe(p,p•y)56Fe react10n, at a pr0t0n ener9y 0f 3.43 MeV, ha5 a150 6een u5ed t0 pr0duce 11near1y p01ar12ed 0.847 MeV ph0t0n51• 4). 7he t1me nece55ary t0 ca116rate a p01ar1meter, 0r t0 mea5ure an a5ymmetry a550c1ated w1th a phy51ca1 pr0ce55 wh1ch 15 5en51t1ve t0 11near p01ar12at10n, t0 a 91ven re1at1ve 5tat15t1ca1 accuracy, 15 1nver5e1y pr0p0rt10na16) t0 1P 1, where 1 15 the 1nten51ty 0f the ph0t0n 6eam and P 15 the de9ree 0f 11near p01ar12at10n (P•< 1). 7h15 5u99e5t5 the u5e 0f 1P 2 a5 a f19ure 0f mer1t f0r the 4ua11ty 0f the ph0t0n 6eam. 1t 15 the purp05e 0f th15 n0te t0 5h0w that, 0n the 6a515 0f th15 f19ure 0f mer1t, 1t 15 advanta9e0u5 t0 u5e h19her ener9y pr0t0n5 and th1ck tar9et5 when the react10n5 24M9(p,p• y)24M9 and 56Fe(p, p• y)56Fe are u5ed a5 50urce5 0f 11near1y p01ar12ed ph0t0n5. 1f the an9u1ar d15tr16ut10n W(0) 0f the y-ray5 15 expre55ed a5
An9u1ar d15tr16ut10n5 and y1e1d5 were mea5ured f0r the react10n5 24M9(p,p•y)24M9 and 56Fe(p,p~y)56Fe u51n9 the pr0t0n 6eam 0f the 4 MV Van de 6 r a a f f acce1erat0r 0f the Nat10na1 Re5earch C0unc11 0f Canada. 7he th1ckne55e5 0f 60th the ma9ne51um and the 1r0n tar9et were 9reater than the ran9e 0f the pr0t0n5. 7he an9u1ar d15tr16ut10n 0f the 1.37 MeV y-ray5 fr0m the react10n 24M9(p,p~y)24M9 wa5 meared at a pr0t0n ener9y 0f 3.07 MeV. An9u1ar d15tr16ut10n5 0f the 0.847 MeV y-ray5 pr0duced 1n the react10n 56Fe(p, p• y)56Fe were mea5ured at pr0t0n ener91e5 0f 3.43 MeV and 3.92 MeV. 7he re1at1ve 1nten51ty 0f the5e y-ray5 em1tted at 90 ° t0 the pr0t0n 6eam d1rect10n wa5 mea5ured 1n the pr0t0n ener9y ran9e 0f 1.95 MeV t0 3.10 MeV f0r the react10n 24M9(p, p• y)24M9 and the pr0t0n ener9y ran9e 0f 2.8 MeV t0 4.0 MeV f0r the react10n 56Fe(p, p•y)56Fe. 7he re5u1t5 are ta6u1ated 1n ta61e 1. 7he m0va61e 6e(L1) c0unter u5ed t0 mea5ure W(0) wa5 5uff1c1ent1y d15tant fr0m the tar9et that c0rrect10n5 f0r the f1n1te 512e 0f the detect0r were ne9119161e ( < 1 % ) . A 5ma11 c0rrect10n wa5 made f0r a650rpt10n 0f the em1tted y-ray5 1n the tar9et 6ack1n9. 7he data f0r the 2.01 MeV and the 2.40 MeV re50nance5 1n 24M9(p,p•y)24M9 are taken fr0m pu6115hed re5u1t54). 7he mea5urement 0f W(0) f0r the react10n 56Fe(p,p•y)56Fe at a pr0t0n ener9y 0f 3.43 MeV 15 1n exce11ent a9reement w1th a prev10u5 re5u1t4). 7he re1at1ve y1e1d5 1 (90 °) are n0rma112ed t0 the 2.01 MeV re50nance f0r the 24M9(p, p•y)24M9 react10n and t0 the y1e1d at 3.43 MeV f0r the 56Fe(p, p• y)56Fe react10n. F19ure5 0f mer1t 1P 2 are 91ven 1n the 1a5t c01umn 0f ta61e 1, w1th e5t1mated accurac1e5 0f 10-20%. 0 n the 6a515 0f the def1ned f19ure 0f mer1t the 4ua11ty 0fthe ph0t0n 6eam pr0duced 6y 3.07 MeV pr0t0n5 and a th1ck ma9ne51um tar9et 15, f0r a 91ven pr0t0n 6eam
W ( 0 ) = 1 + a 2 P2 (0) + a 4 P4 (0),
where P2 (0) and P4(0) are Le9endre p01yn0m1a15, then the 11near p01ar12at10n 0f E2 ph0t0n5 em1tted at 90 ° t0 the pr0t0n 6eam d1rect10n 15 91ven 6y 7) P(90 °) =
1.5 a2 +0.625 a 4
1--0.5 a2 +0.375 a 4" 7hu5, P (90 °) can 6e der1ved fr0m a mea5urement 0f W(0). * 0 n 1eave fr0m: 1n5t1tute ••Rudjer 80~k0v16~, 2a9re6, Yu9051av1a.
149
150
W . R . D1X0N et a1. 7A8LE 1
Character15t1c5 0f ph0t0n 6eam5 pr0duced 6y pr0t0n 60m6ardment 0f th1ck tar9et5 0f M9 and Fe. 7he re1at1ve 1nten51t1e5 1 (90°) and f19ure5 0f mer1t 1p2 are n0rma112ed 5eparate1y f0r each tar9et. Pr0t0n ener9y Ph0t0n ener9y (MeV) (MeV) 2.01 2.40 3.07 3.43 3.92
1.37 1.37 1.37 0.847 0.847
7ar9et
a2
a4
P (90°)
1 (90°)
1P 2
M9 M9 M9 Fe Fe
0.45 0.55 0.33 0.36 0.32
0 - 0.52 0.28 -- 0.23 -- 0.21
0.87 4.0.05 0.94 • 0.08 0.71 4.0.03 0.54 4-0.02 0.45 4. 0.02
1.0 4.0 50 1.0 3.3
0.8 3.5 25 0.29 0.67
CUrrent, appr0X1mate1y 7 t1me5 6etter t h a n the p h 0 t 0 n 6 e a m pr0dUCed at the 2.40 MeV re50nance, a n d appr0X1mate1y 30 t1me5 6etter t h a n the p h 0 t 0 n 6eam pr0dUCed at the 2.01 MeV re50nance. F 0 r the 56Fe(p,p•7)56Fe react10n the 4ua11ty 0f the p h 0 t 0 n 6eam p r 0 d u c e d w1th 3.92 MeV pr0t0n5 15 appr0x1mate1y 2.3 t1me5 6etter t h a n the 6 e a m pr0duced 6y 3.43 MeV pr0t0n5. 7he5e 1mpr0vement5 1n the 4ua11ty 0f the p h 0 t 0 n 6eam5 are part1cu1ar1y 1mp0rtant when 5y5tem5 w1th 10w detect10n eff1c1enc1e5 are 6e1n9 1nve5t19ated a n d they have 6een u5ed advanta9e0u51y 1n 1nve5t19at10n5 0f pr0ce55e5 1n at0m1c phy51c5 w1th 11near1y p01ar12ed ph0t0n58). 7 h e auth0r5 W15h t0 t h a n k M r J. D. 5t1n50n f0r prepar1n9 the tar9et5. 0 n e 0f U5 (8.A.L.) W0U1d a150 11ke t0 t h a n k the Nat10na1 Re5earCh C0UnC11 0f C a n a d a
a n d the At0m1C Ener9y C0ntr01 8 0 a r d 0f C a n a d a f0r f1nanC1a1 a5515tance.
Reference5 1) 6. J. Mcca11um, Phy5. Rev. 123 (1961) 568. 2) 6. 7. Ewan, 6. 1. Ander550n, 6. A. 8arth010mew and A. E. L1ther1and, Phy5. Letter5 298 (1969) 352. 3) 6. E. 0wen and Y. K. Lee, Nuc1. 1n5tr. and Meth. 82 (1970) 173. 4) A. E. L1ther1and, 6. 7. Ewan and 5. 7. Lam, Can. J. Phy5. 48 (1970) 2320. 5) A. Lju61~16 and 8. A. L09an, Nuc1. 1n5tr. and Meth. 99 (1972) 269. 6) 8. A. L09an, R. 7. J0ne5 and A. Lju61(;16, Nuc1. 1n5tr. and Meth., t0 6e pu6115hed. 7) L. W. Fa99 and 5. 5. Hanna, Rev. M0d. Phy5.31 (1959) 711. 8) R. 7. J0ne5, 8. A. L09an, A. Lju61616, W. R. D1x0n and R. 5. 5t0rey, 8u11. Am. Phy5. 50c. 18 (1973) 142.