A EUCENTRIC GONIOMETER HEAD SLIDING ON AN EXTENDED REMOVABLE ARC MODIFIED FOR USE IN CRYOCRYSTALLOGRAPHY

Efficient crystal handling at cryotemperatures requires flexible tools A standard goniometer head has been modified such that it retains euc entricity and allows any position between the coaxial and vertical ori entations relative to a horizontal spindle axis, corresponding to the positions of data collection and crystal transfer, respectively. This is accomplished by a large are on which slides the upper portion of th e goniometer head containing all three translational and one rotationa l degree of freedom. The are can be removed when the head is coaxial w ith the spindle. The head is designed to accept commercially available cryotools In addition, a heat-shield assembly can be installed to pre vent the formation of ice.