Further EC frequencies for ASDEX Upgrade?
AUG Seminar
- Datum: 04.04.2024
- Uhrzeit: 12:20 - 13:20
- Vortragender: Jörg Stober
- Ort: L6 II
- Raum: Seminarraum L6, 2.Stock Süd
Gy5 and 6 are the oldest gyrotrons we are operating and we are considering replacing them soon
by 2 new ones which should be able to deliver 2-2.5 MW into the plasma (together).
Since we hardly use all of the installed 105 GHz gyrotrons at the same time, there is limitted use in just replacing
the old gyrotrons at 105/140 GHz. Additionally, if we use 140 GHz for central heating the 105 GHz are not
absorbed in the plasma. To do so, for example to drive current in the pedestal region,
we have to reduce the field below 2.4 T and we start to lose control on Tungsten.
.
The possible frequencioes are determied by the thicknes of the diamond window.
So far it is 1.8 mm corresponding to 2 lambda (in Diamond). So the next higher frequency is 175 GHz.
This might be interesting for off-axis current drive in AT scenarios.
Our ECRH3 Gyrotrons should in principle be able to operate at that frequency with 0.3 MW per gy, but we never followed that up.
The cold resonance is quite far on the HFS and especially in applications with high Te (as required for current drive)
there is a strong heavily Doppler shifted X3 absorption taking most of the beam power without driving current.
Almost vertical launch is no option in our device.
With those draw backs of 105/175 GHz we should consider thicker windows
with 2.5 lambda or 3 lambda, corresponding to 112/140/168 GHZ resp 116.7/140/163.3 GHz.
This corresponds to a delta_R of the resonances of roughly 33 cm resp. 27.5 cm (41,25 cm for 1.8 mm)
Possible applications and technical boundary conditions will be discussed
including central heating at Bt different from 2.5 T.
I am aware of the additional trouble for micro-wave diagostics,
also worth discussing (after the talk).
Such a decision has to be taken soon and will have consequences
for many years. The gyrotrons which we plan to replace are older than 16 years.
It does not come for free, since this requires also the change of diamond windows at the torus.
So we should only go for this if we see serious applications (which you may contact the speaker with even before the talk, please).
by 2 new ones which should be able to deliver 2-2.5 MW into the plasma (together).
Since we hardly use all of the installed 105 GHz gyrotrons at the same time, there is limitted use in just replacing
the old gyrotrons at 105/140 GHz. Additionally, if we use 140 GHz for central heating the 105 GHz are not
absorbed in the plasma. To do so, for example to drive current in the pedestal region,
we have to reduce the field below 2.4 T and we start to lose control on Tungsten.
.
The possible frequencioes are determied by the thicknes of the diamond window.
So far it is 1.8 mm corresponding to 2 lambda (in Diamond). So the next higher frequency is 175 GHz.
This might be interesting for off-axis current drive in AT scenarios.
Our ECRH3 Gyrotrons should in principle be able to operate at that frequency with 0.3 MW per gy, but we never followed that up.
The cold resonance is quite far on the HFS and especially in applications with high Te (as required for current drive)
there is a strong heavily Doppler shifted X3 absorption taking most of the beam power without driving current.
Almost vertical launch is no option in our device.
With those draw backs of 105/175 GHz we should consider thicker windows
with 2.5 lambda or 3 lambda, corresponding to 112/140/168 GHZ resp 116.7/140/163.3 GHz.
This corresponds to a delta_R of the resonances of roughly 33 cm resp. 27.5 cm (41,25 cm for 1.8 mm)
Possible applications and technical boundary conditions will be discussed
including central heating at Bt different from 2.5 T.
I am aware of the additional trouble for micro-wave diagostics,
also worth discussing (after the talk).
Such a decision has to be taken soon and will have consequences
for many years. The gyrotrons which we plan to replace are older than 16 years.
It does not come for free, since this requires also the change of diamond windows at the torus.
So we should only go for this if we see serious applications (which you may contact the speaker with even before the talk, please).