ELOG MUGAST

Previous Papers - gamma decays from states in the 4-MeV region

2019 paper by Hall, Bardayan, et al., gamma decays of 4.14 and 4.20 states, g-g-t triple coincidences.

Abstract:
The 15O(α,γ)19Ne reaction is responsible for breakout from the hot CNO cycle in Type I x-ray bursts. Understanding the properties of resonances between Ex = 4 and 5 MeV in 19Ne is crucial in the calculation of this reaction rate. The spins and parities of these states are well known, with the exception of the 4.14- and 4.20-MeV states, which have adopted spin-parities of 9/2− and 7/2−, re- spectively. Gamma-ray transitions from these states were studied using triton-γ-γ coincidences from the 19F(3He,tγ)19Ne reaction measured with GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies) at Argonne National Laboratory. The observed transitions from the 4.14- and 4.20-MeV states provide strong evidence that the Jπ values are actually 7/2− and 9/2−, respectively. These assignments are consistent with the values in the 19F mirror nucleus and in contrast to previously accepted assignments.

Noteworthy is that they also don't observe the 3.96MeV transition from the 4.20MeV state, consistent with our observations.

No data is given on the 4.033 MeV state [potentially see further discussion in the corresponding PhD thesis].
From the data, however, it would seem that the (3He,t) reaction does not really populate the 4033 state [otherwise, the 4033 transition should have been seen in Figure 4].

Attachment 1: 1904.00603.pdf

Sat Jul 20 14:00:22 2019

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Run : 117
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Start at 2019-07-20 13:59:36.817451

H2O cold box reset. took a while to reach below 20deg in cave.
beam back.

Stop at 2019-07-20 16:47:36.880786
Stop comment: VXI VAMOS LOST

Sat Jul 20 14:21:22 2019

Nikola

ONLINE

screenshots run 117 @ 14h20

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Beam profile & intensity (run 117 @ 14h30)

Sat Jul 20 14:32:18 2019

Beam intensity: 1.4e7 pps
VAMOS: ~ 1200

Attachment 1: IMG_20190720_142852.jpg

Sat Jul 20 17:00:19 2019

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Run : 118
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Start at 2019-07-20 16:59:33.086411

Start after the overtemperature of VXI VAMOS.

Stop at 2019-07-20 21:11:28.272749
Stop comment: Vamos VXI offline

Sat Jul 20 17:03:23 2019

Run 117 stopped because VAMOS VXI went offline

Sat Jul 20 17:06:12 2019

Start run 118

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Run 118 screenshots @ 19h14

Sat Jul 20 19:12:58 2019

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Marlene, Nicolas, Christian, Fairouz

Sat Jul 20 19:21:56 2019

OFFLINE

Trying to understand AGATA g-ray yields

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?)?

Sat Jul 20 19:23:37 2019

Ex in 19F from run 72

Data: Total integral for peak region around 4 MeV in 19F during run 72:

~35 average peak height over 27 bins = 945 counts. Note that this includes what looks like background in the spectrum. In reality, however, this should be considered part of the yield, because the 1.5 MeV , 4.0 MeV peak, and 5.5 MeV peaks just about touch, and are about the same intensity. So realistic integral is approximately the number of counts between 2.8 and 4.8 MeV.

Comparison to previously observed cross section [F. de O.]:

Ex = 3.999+4.033 [19F]
d-sigma/d-Omega ~ 3.5mb/sr (approximately constant over the range of 0-20 deg c.m.

d-Omega = 0.061 sr [over 0-20 deg. c.m]
=>
sigma = 0.21mb

Assumed efficiencies:
e_MUGAST = 0.5
e_charge-state = 0.5
e_VAMOS = 0.8 [intrinsic]

d_tgt = 337ug/cm2 [7Li component]

Run72:
beam = 1e8pps
run time = 2.4h

Total reaction rate = 2.2k/h
Coincidence detection rate = 440/h
Coincidence detection yield over 2.4h [run72] = 1056

Consistent with the observation for MUGAST-VAMOS coincidences for the run.

Beam intensity is decreasing.

Sat Jul 20 19:24:31 2019

The beam intensity decreased by half since 19h00 (600 in Vamos-or)due to the primary beam.
The operators are working on it since.
The intensity of 10^7 pps came back at 8 pm.
Intensity measurement with the profiler 1.1x10^7 pps for Or-Vamos=1100

Run 118 stopped because VXI Vamos turned offline because of overheat

Sat Jul 20 21:10:57 2019

Run 118 stopped because VXI Vamos turned offline of overheat

Sat Jul 20 23:18:02 2019

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Run : 119
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Start at 2019-07-20 23:17:24.464827

Start after SECOND overtemperature of VXI VAMOS.

Stop at 2019-07-21 20:12:21.834156
Stop comment: stopped because intensity dropped to 6e6 pps (profiler) PCP working on optimization

Sat Jul 20 23:32:44 2019

Sylvain Fairouz

OFFLINE

Trying to understand AGATA g-ray yields

Marlene, Nicolas, Christian, Fairouz wrote:

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

Run 119 (Problem with VXI fixed for the moment)

Sat Jul 20 23:43:02 2019

Run 119.
Or-Vamos= 1430 ---> I=1.43x10^7 pps

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Sat Jul 20 23:57:34 2019

Diego

OFFLINE