====== A first look at a month of data from the GAGG ====== //2024/2/27, AndreaM// \\ We analyse roughly one month of data acquired with the GAGG underground, from 2024/1/15 to 2024/2/12. The dataset is **29 days** long, the total number of acquired events is 38193181, which corresponds to a rate of ∼15 Hz. \\ We consider the discrimination parameter //normamplitude// η=Amplitude/Integral and we define the β/γ and α bands as follow: * β/γ : 0.03 < η <0.1 * α : 0.01 < η < 0.03 The 2D plot in Figure 1 shows η vs Integral for the events. ^ Figure 1 ^^ ^ Total 2D plot η vs Integral ^ Zoom-in for Integral<82000 ^ | {{:gagg-nd:20240227_2dspectrum_0.png?600|}} | {{:gagg-nd:20240227_2dspectrum_1.png?600|}} | The large majority of the events (96%) is falling in the β/γ band. Beyond ²⁰⁸Tl peak there is a first population of order 900 events probably due to the overlap of the 2.6 MeV γ with another lower energy γ (583 keV, 511 keV,...). Then there is another population (only 8 events) around Integral = 150-200*10³ which maybe is due to other γ overlaps or are we seeing some first γ from Gd-n capture?\\ //NOTE:// The range 150-200*10³ in ADC counts corresponds to 5.8-7.7 MeV (as shown later in the note).\\ ** The β/γ band.**\\ ^ Figure 2 ^ | {{:gagg-nd:20240227_bgspectrum_0.png?600|}} | We recognize two clear peak in this spectrum: one around 40*10³ which is due to the 1.5 MeV ⁴⁰K decay and one at 70*10³ from the 2.6 MeV ²⁰⁸Tl decay. Even if **very preliminary**, we can try a simple gaussian fit of these peaks. ^ Figure 3 ^^ ^ ⁴⁰K fit ^ ²⁰⁸Tl fit ^ | {{:gagg-nd:20240227_40kfit_0.png?600|}} | {{:gagg-nd:20240227_208tlfit_0.png?600|}} | **Just to have a feeling**, the following table reports the fit result and the first estimation of the energy resolution. ^ Peak ^ Energy [MeV] ^ Fit Mean [ADC] ^ Fit Sigma [ADC] ^ Energy Scale from fit [ADC/MeV] ^ Energy Resolution (Sigma/Mean) [%] ^ | ⁴⁰K | 1.5 | 38100 | 1126 | 25400 | 2.9 | | ²⁰⁸Tl | 2.6 | 68060 | 1600 | 26180 | 2.3 | **The α band.** ^ Figure 4 ^ | {{:gagg-nd:20240227_aspectrum_1.png?600|}} | For the α events we have to consider a quenching effect. We can try to have a first estimation looking at some characteristic peaks of the α spectrum. * The narrow peak below 10⁴ is due to the α-decay of ¹⁵²Gd at 2.2 MeV. This represents the dominant feature in the α spectrum. * The peak slightly below 2*10⁴ is probably a mixture of the ²³⁸U α-decays at 4.2 and 4.15 MeV. In the left tail some other α-decay is probably present, maybe the ∼4 MeV decays from ²³²Th. * The peak between 2-2.5*10⁴ can be tentatively attributed to ²³⁴U decay at 4.78 and 4.72 MeV. * Finally with the delayed coincidence analysis we have identified the peak between 3.5-4*10⁴ as due to ²¹⁶Po α-decay at 6.8 MeV.\\ We can try again a simple gaussian fit of these 4 peaks.\\ ^ Figure 5 ^^ ^ ¹⁵²Gd [2.2 MeV] ^ ²³⁸U [4.2 MeV] ^ | {{:gagg-nd:20240227_152gdfit_0.png?600|}} | {{:gagg-nd:20240227_238ufit_0.png?600|}} | ^ ²³⁴U [4.8 MeV] ^ ²¹⁶Po [6.8 MeV] ^ | {{:gagg-nd:20240227_234ufit_0.png?600|}} | {{:gagg-nd:20240227_216pofit_0.png?600|}} | The following table summarises the results of the fit, with a tentive estimation of the quenching effect with respect to the energy scale derived from the β/γ band (∼26000 ADC/MeV). ^ α Peak ^ Energy [MeV] ^ Fit Mean [ADC] ^ Fit Sigma [ADC] ^ Energy Scale from fit [ADC/MeV] ^ Quenching ^ | ¹⁵²Gd | 2.2 | 8452 | 347 | 3842 | 0.15 | | ²³⁸U | 4.2 | 19340 | 864 | 4605 | 0.18 | | ²³⁴U | 4.8 | 23150 | 818 | 4823 | 0.18 | | ²¹⁶Po | 6.8 | 37430 | 1300 | 5504 | 0.21 | **Next steps**\\ - Detailed study of α-α and α-γ delayed coincidences - Conversion of ADC counts in number of PE - Improve the discrimination parameter η - AmBe calibration to see neutron captures - Calibration with γ sources for detailed energy scale and resolution studies (?)