ELOG MUGAST

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

This search was triggered by our lack of seeing the 3958keV line at the expected level. 2689 keV line observed (runs 112,115,116) as 55-60 counts. Expected yield in 3958 keV line based on 80:20 branching and 1.5:1.0 efficiency is 10 counts. We see (at most) 2 in the full photo-peak for this line. (Theses two counts are also lower than expected by about 20 keV.)

The 4.20 MeV to 0.24MeV line in the attached spectrum (p. 2 of J.M.Davidson & M.L.Roush) is one of three spectra by them, on which this branching ratio was based. With the level of detail in these spectra, I think it is fair to question this result. NNDC and TUNL data for branching ratios of this state is entirely based on this paper.

Action: other branching ratios in this region should be checked in this paper to see whether there could be other dubious branchings.

Sat Jul 20 12:06:00 2019

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

Further to the previous post on gamma-ray lines, attached is Kanungo's paper on doppler-attenuation measurement of the 4033 line for lifetime measurement. The lower-energy lines are, however, not included in the figures.

Sat Jul 20 12:57:41 2019

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].

Sat Jul 20 14:21:22 2019

Nikola

ONLINE

screenshots run 117 @ 14h20

Marlene, Nicolas, Christian, Fairouz

Sat Jul 20 19:21:56 2019

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 23:32:44 2019

Sylvain Fairouz

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

Sat Jul 20 23:57:34 2019

Diego

VAMOS acceptance, comparison between 9+ and 10+ states

Figures above, simulation of VAMOS acceptance for 10+ and 9+ 19Ne charge states. Ratio between them quite big (0.58)
Figures below, comparison of the states with offline data. Ratio much smaller.
It seems like acceptance doesn't cut the 10+ charge state too much, but 10+ is less produced than 9+.

Sun Jul 21 14:54:28 2019

Sun Jul 21 16:39:38 2019

Marl�ne, Antoine

BEAM

IMPORTANT :How to send scalers to PCP

Go to PCP

Open a terminal
> ssh -X mugast@ganp154
passwd : Spiral1+

> ./LaunchScalers.sh

Sun Jul 21 16:42:20 2019

Marl�ne

Conversion of data from AGATA :update

When VAMOS VXI crashed (run 118) the Action file was recompiled.
As AGATA conversion is not copying the ACTION file for each run, it used the old version by default (from 16th of july).

We have modified the do_global_replay.sh so that it takes the ACTION file from the Replay directory where we have copied the ACTION file for run_0119.

So for conversion of file before run 119, the ACTION file in the zworkingDir of AGATA should be used.
For all conversion of runs after run 119, the ACTION file in the Replay directory should be used.

Marl�ne, Christian, Ksenia

Sun Jul 21 16:51:30 2019

BEAM

trial of tracking of the implantation of 15O

Looking at AGATA count rate, we have seen that the highest counting rate for 511 keV line is seen in the inner ring (0*A clusters).
The outer ring detectors (10B for example) counts 10 times less.

Our conclusion is that the beam is partly implanted at the entrance of MUGAST chamber.
The outer ring probably sees the implantation on MUST2 masks.

A more refined analysis is needed to backtrack where the 15O are implanted.

Sun Jul 21 17:02:25 2019

Marl�ne

BEAM

beam intensity in the afternoon

Sun Jul 21 17:45:54 2019

kseniia

AGATA

Current total stats on 19Ne

Stats from runs 112, 115, 116, 117, 118, 119(~15h)
beta = 8%
Q = 9 & 10

Sun Jul 21 17:57:08 2019

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

In comment to previous entry (see thread), on the 2019 Hall paper on 19Ne transitions:

Note that Fig 4.c is described as: Gated on the 238-keV 5/2+ to ground-state transition. The 3897.5-keV transition from the 4141.8-keV state is observed for the first time. This means the spectrum is designed such that it wold not show the 4033 transition. Therefore, whether they are sensitive to this is an open question. See also PhD thesis of Hall for further details?

Sun Jul 21 22:28:11 2019

Attached is the intensity distribution of 511 keV in run 119 (first image) vs run 120 (second image).
In between the two runs, beam optics was twitched.

These are the segments of crystal 02A which is near the beam pipe. Bottom is the tip of the detector, top is the
tail.
In run 119 it looks that the pillars that are near the beam line (columns 4 and 5) were seeing 511 more or less
homogeneously, which means that we are implanting 15O all over the pipe.
In run 120 looks like we still implant in the pipe, but also we implant a lot more at the target level.

Sun Jul 21 23:18:25 2019

Kseniia

AGATA

Current total stats on 19Ne

Runs 112, 115, 116, 117, 118, 119, 120 and ~1h of 121

We see 3 peak candidates with energies not matching anything known

Mon Jul 22 10:10:02 2019

Previous Papers - alpha-branching ratios for states in the 4-MeV region

Branching ratio data overview from Tan et al. (PRL 2007, attached):
Ex/MeV B_alpha
4.03 2.9(21)e-4
4.14/4.20 1.2(5)e-3
4.38 1.2(3)e-3
4.55 0.07(2)
In the spectra so far, we are very clearly seeing the 4.14/4.20 MeV doublet. We may also be seeing some indication of the 4.38, 4.55 and/or 4.60 MeV states above 4 MeV (4.14, 4.27, and 4.36 MeV respectively, as dominant lines). Note that we have no alpha-branching-ratio data for the 4.60MeV state, and that most likely the gamma-ray events we currently see above 4MeV are the 4.14MeV and 4.36MeV lines (4.38 and 4.60 MeV states).

Comments to lifetimes from Mythili et al., (PRC 2008, attached). The relevant lifetimes are for the states between 4.14 and 4.55. Only dominant errors are given, for details, see attached table:
Pre-2008 Mythili
Ex/MeV lifetime/fs lifetime/fs
4.14 18(+2/-3) 14(4)
4.20 43(+12/-9) 38(+20/-10)
4.38 5(+3/-2) <5.4 (95% CL)
4.55 15(+11/-5) 19(4)

In combination:
4.38 MeV: Branching ratio is fairly well known. Lifetime is very poorly known, if at all. We have 7 counts so far (provisional), in the 4.14 MeV peak after about 3 days of beam on target.
4.55 MeV: Branching ratio is fairly well known. Lifetime is fairly well known, but it is not clear that we see this decay.
4.14/4.20: Lifetimes is known reasonably well for 4.14, poorly for 4.20, and differ by about a factor of 2-4 (within error). Branching ratio is only known in combination between the two. This complicates normalisation to these two states greatly, as we would in principle have to assume any combination of this contribution from 4.14, 4.20, or combined. In their paper (Tan 2007), they do state for this measurement that: "The measured􏰑 peak [in the alpha-spectrum] seems to be lower in energy than the simulated one, indicating that these decay events are more likely from the 4.14-MeV state.". Looking at the spectrum they refer to, however, I would not say that this is in any way a clear cut argument (and they do state it with some hesitation).

In summary: because of the overlap of the 4.14 and 4.20 states in the branching ratio data [which I should admit that I had missed when investigating the previous data and results earlier] it will be much harder than expected to cross check normalisation of the data based on the observed lifetimes and alpha branching ratios for 19Ne resonances.

Mon Jul 22 11:21:25 2019

Pedestals of MG3_X have changed yesterday, they are back to about 8200 as they should be --> saved in ped_muvi2sec2_22072019_new
We are using wrong pedestals (of about 9600) --> the pedestals are saved under mugast account as ped_muvi2_sec2_22072019_sameas_1807219

We kept the same pedestals but we reduced the pedestal suppression to 0 - 6800 in order not to suppress the data of one other 2 mates.
The attached spectrum shows that all the X of MG3 are recovered (although the impact matrix still does not work)

Mon Jul 22 12:33:17 2019

Full stats for runs 112..124 with the event-by-event Doppler correction. So, we see 4140 kev.
Also, the betas of all the 19Ne with Q= 9,10 identified in VAMOS

Mon Jul 22 12:54:25 2019

Kseniia

AGATA