Sample mounting
Page 3 of 7
Metal crystals
![]() |
Polished metal single crystals are usually mounted on Ta heating wires (diameter 0.25 or 0.4 mm) annealed by passing current. Round shape and 5-10 mm diameter is optimal, the thickness in the range 1-2 mm. The smaller the crystal the higher annealing temperatures can be easily reached. The annealing limit for small and thin crystals (5 mm diameter) is about 1100 °C/1400 K, larger crystals (10 mm diameter) will hardly reach 700 °C/1000 K. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
![]() |
The crystal should have 2 slits (0.3-0.5 mm width). If not it can be spot-welded directly to the heating wires (only some materials). Spot-welding improves the heating contact and provides easier annealing and cooling. The thermocouple can touch the crystal from the backside like a spring or be spot-welded to the crystal (only some materials). Spot-welding improves the thermal contact and provide more precise temperature reading. The error can be up to 100 K/°C. For annealing usually the 70 V×24 A DC power supply is sufficient. Maximum annealing current is 20 A. The centre of the sample is theoretically at half of the annealing voltage so it is difficult to acquire spectra during annealing |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
![]() |
Example of Cu crystal (8 mm diameter × 2 mm thickness) mounted. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
![]() |
Example of Ir crystal (5 mm diameter × 1 mm thickness) mounted. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
![]() |
Assembly:
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
![]() |
For the correct thermocouple pin contact the pins must stick out 3.8-4 mm below the baseplate bottom surface. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
![]() |
For the correct connection the annealing contacts must be 3.6-3.8 mm above the baseplate top surface. This distance (if 3.5 mm or lower) can be increased by placing tiny spacers made of properly thick wire below the bottom ceramic spacers (3a) or swapping the thin ceramic spacers (3a) with the thicker ones (3b). Check in the areas labelled by green circles that the (too big) sample (S) is not touching directly the annealing contacts (7ab). In such case the annealing current would not flow through the thin annealing wires (8) but directly through the thick crystal (S) which would make the annealing inefficient and high temperatures could not be reached. |
Last Updated on Thursday, 09 March 2023 10:32