$$B\rho $$-defined isochronous mass spectrometry and mass measurements of $$^{58}$$Ni fragments
M. Zhang, Xianming Zhou, M. Wang, Y. H. Zhang, Yu. A. Litvinov, X. Xu, R. J. Chen, Huiyong Deng, Chuancheng Fu, Wenwei Ge, H. F. Li, Ting Liao, S. Litvinov, P. Shuai, Jian Shi, R. S. Sidhu, Y. N. Song, M. Z. Sun, Shinji Suzuki, Qiuhong Wang, Y. M. Xing, X. Xu, Takayuki Yamaguchi, X. L. Yan, Jiancheng Yang, Youjin Yuan, Q. Zeng, Xianming Zhou
Abstract
Abstract A novel isochronous mass spectrometry, termed as $$B\rho $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>B</mml:mi> <mml:mi>ρ</mml:mi> </mml:mrow> </mml:math> -defined IMS, has been established at the experimental cooler-storage ring CSRe in Lanzhou. Its potential has been studied through high precision mass measurements of $$^{58}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mn>58</mml:mn> </mml:msup> </mml:math> Ni projectile fragments. Two time-of-flight detectors were installed in one of the straight sections of CSRe, thus enabling simultaneous measurements of the velocity and the revolution time of each stored short-lived ion. This allows for calculating the magnetic rigidity $$B\rho $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>B</mml:mi> <mml:mi>ρ</mml:mi> </mml:mrow> </mml:math> and the orbit length C of each ion. The accurate $$B\rho (C)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>B</mml:mi> <mml:mi>ρ</mml:mi> <mml:mo>(</mml:mo> <mml:mi>C</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> function has been constructed, which is a universal calibration curve used to deduce the masses of the stored nuclides. The sensitivity to single stored ions, fast measurement time, and background-free characteristics of the method are ideally suited to address nuclides with very short lifetimes and smallest production yields. In the limiting case of just a single particle, the achieved mass resolving power allows one to determine its mass-over-charge ratio m / q with a remarkable precision of merely $$\sim 5$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mn>5</mml:mn> </mml:mrow> </mml:math> keV. Masses of $$T_z=-3/2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>z</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>-</mml:mo> <mml:mn>3</mml:mn> <mml:mo>/</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:math> fp -shell nuclides are re-determined with high accuracy, and the validity of the isospin multiplet mass equation is tested up to the heaviest isospin quartet with $$A=55$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>A</mml:mi> <mml:mo>=</mml:mo> <mml:mn>55</mml:mn> </mml:mrow> </mml:math> . The new masses are also used to investigate the mirror symmetry of empirical residual proton-neutron interactions.