Speakers
Description
Measurements of cross section and their extrapolation to stellar conditions are now routinely performed with accuracy of 5% or better. But the formation of $^{16}$O in the fusion of helium with $^{12}$C, in the $^{12}$C($\alpha,\gamma$) $^{16}$O reaction, is still not known with sufficient accuracy, in spite of the central role that this reaction plays in stellar evolution theory. The Warsaw-UConn-SHUBU-ELINP collaboration, developed a new method to measure this cross section by measuring with (mono-energetic) gamma-beams the inverse process of the photo-dissociation of $^{16}$O to $^{12}$C and an alpha-particle. The measurements are performed at the HIgS facility using TPC detectors [1,2] operating with CO$_2$ gas, hence also serving as an active target TPC (AT-TPC).
We will discuss initial measurements with an optical readout TPC (O-TPC) [1] that demonstrated the viability of our method [3] and recent results obtained in 2022 [4], with an electronic readout TPC detector (eTPC) [2]. Briefly, the UConn-TUNL (2012) measurement with an O-TPC allowed us to bench mark the measurement with a TPC against the world data on the $^{12}$C($\alpha,\gamma$) reaction [3], as well as to demonstrate viable measurements of angular distribution over the entire 0º-180º angular range. The recent Warsaw-UConn-SHU-BUELINP measurement [4], with the considerably improved Warsaw-TPC detector, including 1,024 channels of electronic readout, allowed for an energy scan with nominal energies E$\gamma$ = 13.9 MeV to 8.51 MeV (nominal Ecm = 1.35 MeV) [5], to be presented here. Automated data analyses with an application of machine learning technology [5,6] is in progress. We intend (PAC 2023 approved LOI) to continue with measurements at the HI$\gamma$S at lower energies, with the anticipated beam intensity in excess of 109 $\gamma/s$ inside the TPC.
Supported in part by the U.S. Department of Energy grant no. DE-FG02-94ER40870 and National Science Centre, Poland, contract no. 2019/33/B/ST2/02176.
[1] M. Gai, M.W. Ahmed, S.C. Stave, W.R. Zimmerman, A. Breskin, B. Bromberger, R. Chechik, V. Dangendorf, Th. Delbar, R.H. France III, S.S. Henshaw, T.J. Kading, P.P.
Martel, J.E.R. McDonald, P.-N. Seo, K. Tittelmeier, H.R. Weller, and A.H. Young. JINST 5, 12004 (2010).
[2] M. Ćwiok, M. Bieda, J.S. Bihałowicz, W. Dominik, Z. Janas, Ł. Janiak, J. Manczak, T. Matulewicz, C. Mazzocchi, M. Pfützner, P. Podlaski, S. Sharma, M. Zaremba, D. Balabanski, A. Bey, D.G. Ghita, O. Tesileanu, M. Gai, Acta. Phys. Pol. B 49, 509 (2018).
[3] R. Smith, M. Gai, S. R. Stern, D. K. Schweitzer, M. W. Ahmed, Nature Communications 12, 5920 (2021).
[4] M. Ćwiok, W. Dominik, A. Fijałkowska, M. Fila, Z. Janas, A. Kalinowski, K. Kierzkowski,
M. Kuich, Ch. Mazzocchi, W. Okliński, M. Zaremba, M. Gai, D.K. Schweitzer, S.R. Stern,
S. Finch, U. Friman-Gayer, S.R. Johnson, T. Kowalewski, D.L. Balabanski, C. Matei, A.
Rotaru, K.C.Z. Haverson, R. Smith, R.A.M. Allen, M.R. Griffiths, S. Pirrie, and P.S.R
Alcibia, EPJ Web Conf. 279, 04002 (2023),
[5] Mikołaj Ćwiok et al., contribution to this conference, Nuclear Photonics 2023.
[6] Robin Smith et al., contribution to this conference, Nuclear Photonics 2023.
