assignment1.pdf

NUST, SEECS

Assignment 1

Sara AfzalNUST201362877MSECCS61213F

February 23, 2015

1 PRECISION MASS MEASUREMENT OF ARGON ISOTOPES

In this experiment a precision mass measurement of the isotopes Ar 32, 33, 34 is proposed.Mass values of these isotopes are of importance for various calculation of constants and cor-rections which are of great use.The measurements were carried out with the ISOLTRAP Penning trap mass spectrometerat ISOLDE.It consists of a linear RFQ ion cooler and buncher and two Penning traps. TheRFQ ion cooler and buncher efficiently converts continuous ISOLDE beam into cooled ionbunches. These bunches are captured in the first Penning trap, which can be operated asan isobar separator. The ions are again cooled then sent to the second Penning trap, whichis the actual mass spectrometer, where mass measurement is carried out. The Penning traptechnique offers the unique advantage, that the ions are stored in a very small volume andthat the electromagnetic fields can be very well controlled. Hence, systematic errors are verysmall. The largest contribution is the stability of the magnetic field. If a magnetic field cali-bration is performed every 2-3 hours then the systematic error can be constraint to to a levelof a few 10−8.

• The mass of Ar 32 is known with an uncertainty of 50 keV. It also have a half life of100ms. Using ISOLTRAP Penning trap mass spectrometer we have determined themass of Ar 32 with the desired accuracy of about 3 keV.

• Ar 33 which has a half-life of only 173 ms and the uncertainty for the mass value ofAr 33 is known to be 4.2 keV, which is further improved by a factor of 2 to reach 2 keV.

• The mass of Ar 34 is presently known with an uncertainty of 3 keV. As its half life is 845ms so the achieved mass uncertainity is less than 1 keV.

1