First experimental results from lithium powder injection on ST40

A multi species impurity powder dropper (IPD) has recently been installed on ST40 and used to inject lithium granules. Boron granules were also injected in a small subset of pulses. In the highest performance pulses where the dropper was used, Ip~750kA, BT~2.1T, ne0~1e20/m3, Te0~2keV, ~1MW NBI at 55keV, lithium had no measurable effect on any core parameter: stored energy, Zeff, Te, ne, solenoid volt*second consumption, or soft X-ray emission. By contrast, in lower performance pulses, Ip~390kA, BT~1.5T, ne0~7e19/m3, Te0~1.5keV, ~1MW NBI at 55keV, lithium advanced the entry into H-mode and had some effect on the ELM activity before the plasma entered ELM free H-mode, all with no measurable change in Zeff. Scanning the quantity and timing of lithium injection, we found that injecting more lithium earlier in the pulse further advances the H-mode entry. We were unable to inject 'too much lithium' and with the maximum injection did not observe any reduction in core performance. We will also present planned upgrades for the next lithium campaign where an evaporator will be used.