All further colloquiua are scheduled under the W7-X Divertor Concept Development:
https://event.ipp-hgw.mpg.de/category/63/
You can add these events to your calender with the following link:
https://event.ipp-hgw.mpg.de/category/63/events.ics?user_token=61_ua15M4a2Hqdv8pOPUfYmditClSgPxgtZmIiM1ym-rx4
Please let me know if you’d appreciate an additional weekly reminder, or separate calender entry only for the colloquiua.
In the sense of process optimization, I’d also like to ask you for your constructive criticism on how we can make these discussion more efficient and more valuable for you.
I understand the continued concern on how to publish this work. Moving forward, I would like to neglect this aspect and put the focus on the task.
Goal: Design a divertor
For this I need to
- Define
- Define a divertor
- Define and categorize divertor requirements
- De-couple function into a priori first principles
- Define metrics with statistical analysis for individual functions
- Measure Metrics
- Analyse Metrics
- Improve functions
- Control and validate improvement
The goal of my current work is part (I) - the definition.
Part (II) and (III) I have done in the last two years. Part (IV) and (V) are future work.
Yesterday we discussed I.a and started on I.b.
- In a fusion reactor, He has to be removed continuously. To be removed, alpha particles have to be neutralized. In a Limiter, a target is placed inside the magnetic toroid, limiting the poloidal extend of the plasma toroid and defining the last closed flux surface.
- In a divertor the plasma is diverted away from the plasma toroid before neutralization. This is achieved by creating at least one other magnetic toroid, resulting in an X-Loop in between. We have defined the precise borders between the volumina of Core, Edge, Common flux region consisting of Plasma-SOL and Divertor-SOL, as well as the private flux region. The PFR is only connected by the X-Loop to the plasma toroid. MHD breaks down at the X-Loop and only diffusive and turbulent transport across is possible.
- Mandatory requirements: Giving absolute values for the mandatory requirements is inconsistent with the a priori and statistical approach that I chose, as these absolute values are based on further (material & technology) assumptions.
- A divertor must survive the heat received from the incoming particle flux recombining on the target surface or in the volume, radiation, and neutrons. While heat transport in the plasma can also be convective, heat transfer from the plasma sheath to the divertor target is conductive through particles.
- Our target will have a maximum heat flux q_max[MW/m²] that it is designed for.
- The plasma temperature at the target has to be below a certain T_e to minimize sputtering. This is important for 2 reasons: Extensive sputtering can erode material to the point of target destruction. Sputtering is an impurity source which has to be screened from the core. I will work on a statistical metric for the sputtering related T_e.
- The target has to survive the neutron dpa exposed to.
Performance requirements:
- The He exhaust flux must equal the Alpha production rate. We want to minimize the impurity transport in the core. For this we want to
- maximize the exhaust efficiency, and
- on a second order the screening efficiency. The screening efficiency can be separated into screening in the edge, plasma SOL, divertor SOL, and PFR.
- We briefly touched on the requirement of density control
We stopped the discussion at this point. Next week we’ll continue with the performance requirements.
Do you have any other performance requirements that I should already add?
Goal for next week is to finish the divertor requirements and I will then introduce the a priori first principles and we will go through them individually.
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