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 Sat Jul 20 19:21:56 2019, Marlene, Nicolas, Christian, Fairouz, e768s, OFFLINE, General, Fixed, , Trying to understand AGATA g-ray yields
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 Sat Jul 20 23:32:44 2019, Sylvain Fairouz, e768s, OFFLINE, General, Fixed, , Trying to understand AGATA g-ray yields
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Message ID: 5205
Entry time: Sat Jul 20 23:32:44 2019
In reply to: 5200
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| Author: |
Sylvain Fairouz |
| ExpNbr: |
e768s |
| Type: |
OFFLINE |
| Category: |
General |
| Status: |
Fixed |
| Target-Source: |
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| Subject: |
Trying to understand AGATA g-ray yields |
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| Marlene, Nicolas, Christian, Fairouz wrote: | goal: we want to check whether the yields of the 1297.7 keV (from 19Ne 1536, 3/2+, l=1 state) and 1340 keV (from 19Ne 1615, 3/2-, l=2 state) g-ray lines is compatible with what we expect from x-sec calculations
conditions: we consider runs 112, 115 and 116
observations:
N(1297) = 17 g-rays
N(1340) = 23 g-rays
remarks:
Given x-sec from mirror nucleus (Francois 15N(7Limt) paper) we expect N(1340) >~ N(1297)
ingredients:
1. beam normalization
We use the TAC_FPMW_HF as a proxy. During the same time we integrate the prompt peak and compare the integrated OR VAMOS scaler, we find Scaler(OR VAMOS)/N(TAC) = 193.
We use the comparison of the OR VAMOS (pps) and the beam profiler (pps), we find profiler/OR VAMOS = 1e4
We obtain (2.17e5 + 6.44e4 + 3.52e5)*193*1e4 = 1.2 e12 15O incident particles (at profiler position!)
2. target thickness -> known to be 1.25 mg/cm2 of LiF (RBS measurement)
N(Li) = 1.25e-3 / (19+7) * 6.02e23 at/cm2
3.efficiencies
AGATA @ 1.3 MeV -> 7.5 %
VAMOS intrinsic -> 67 % (Eff_Check.C macro applied to run 116)
MUGAST -> 50 % (lab, geometry), needed because MUGAST is the main trigger
4. 19Ne charge state
we assume 40 % for 9+
5. g-ray branching ratio -> taken from NNDC
6. cross-section
we calculate differential cross section for the 1536-keV 19Ne state (FRESCO, FR-DWBA)
-> at 0 deg, ds/dW =
-> integrated x-sec in VAMOS acceptance (4 deg (lab) -> 20 deg (cm)) = 445 micro barn (C2Sa = 1)
-> taking into account know spectroscopic factor form analog state -> 89 micro barn
Conclusion:
for the 1536-keV 19Ne state we obtain 30 g-rays, instead of 17.
Discussion:
This factor of two could be well within the mirror symmetry assumption. However it seems it is also the case for the 1615-keV 19Ne state, so would not it be a systematic error with a factor of two missing somewhere (beam transmission between the profiler and the target? deficiencies?)? |
We have investigated quickly the 15N(7Li,t)19F reaction based on run 0072. (gamma spectrum corresponding to all run data and with doppler correction with beta 0.08 can be found in /data/mugastX/mugast/acquisition/root/Run72_19Fe_8p.root)
To simplify the analysis the TS were restricted from 46000s to 52000s (/data/mugastX/mugast/acquisition/root/Run72_19Fe_8p_TSGate.root). The beam intentisty was assumed constant and equal to 1.e8 pps (for a total of 6.e11 beam like particle)
The 3/2+ and 3/2- states in 19F produce respectively 1356keV and 1348keV gamma. Counts were estimated roughly with double gaussian fit to be equal to
I(1348) = 21.9 counts
I(1256) = 16.4 counts
Assuming all others parameters are comparable with the previous analysis the counting obtained seems consistent with the measured Salpha=0,2 in previous experiment, Everything seems ok based on this very rough first analysis |