GRETINA is a new detector that has been setup and is working in tandem with the S800 Spectrograph in the S3 vault. A collaborative effort between many laboratories and institutions throughout the United States, GRETINA is spending its summer conducting experiments at NSCL before moving on to another laboratory to be utilized by its facilities.
A new type of gamma-ray detector to study the structure and properties of atomic nuclei, GRETINA is built from large crystals of hyper-pure germanium and will be the first detector to use the recently developed concept of gamma-ray energy tracking. The device consists of 28 highly segmented coaxial germanium crystals, each of which is segmented into 36 electrically isolated elements. Four crystals together are combined in a single cryostate to form a quad-crystal module. With seven modules in total, the modules are designed to fit a close-packed spherical geometry that will cover one quarter of a sphere.
And now, you can see GRETINA take shape at NSCL.
This stop-action video puts photos taken during several weeks of construction and use of GRETINA. Setup occurred beginning in May of this year, culminating in commissioning and its first full experiment, which happened late in July. That experiment sought to reduce the effect of the uncertainty in the 57Cu(p,γ)58Zn stellar reaction in the calculation of the light-curve emitted in X-ray bursts. GRETINA was used to measure gamma rays from the de-excitation of excited states in 58Zn populated by a (d,n) transfer reaction.
The study of the 57Cu(p,γ)58Zn reaction will allow for better models of X-ray bursts since at high bursts temperatures, rp-processing beyond 56Ni is determined by that reaction. The current uncertainty in the reaction covers two orders of magnitude since there are unknown energy levels in 58Zn.
But GRETINA’s beauty isn’t just in the science that it will help unlock. The device itself is wonderful to look at, as the video below will attest to. Enjoy!