Replies to SpanishRFQ Questions

(slides re-used from previous talks)

Points Raised by Juan Luis Muñoz (questions_FETS_17nov2010.pdf)

• “Looking at a 2m model, RF power concentrates at ends. So cannot assume 2.5kW equally distributed in each 0.5m section”

• “Power increases at ends a lot when mirroring vacuum slots”

• “Should be using about 4.5kW at end sections and less toward centre”

Matcher Geometry

Plane vanes Matcher On

Effect of Matcher on Long. Fields

Matcher Off: Fields peak at ends

Matcher On: Fields peak at centre

E-field

E-field

B-field

B-field

Four Metre RFQ Field Flatness

Cold Model Field Flatness

Summary of Reply to Juan• Drastic change when adding a few extra vacuum

slots doesn’t sound realistic. Maybe the mesh was compromised in vane-tip region by needing to mesh the extra slots?

• The EM fields do seem to distribute themselves in interesting ways along the entire 2m length! However we’ll aim to achieve good field flatness so there are no peaks at ends.

• 2.5kW per 0.5m section is based on 80kW average power in RFQ. We have already allowed at least 25% safety margin by using this figure.

Comments on Ana Megia’s Work (1)

(RFQ-1010-05_Megia.pdf andRFQ cooling ESSB _extended.pdf)

• Squirt nozzle mechanical design looks nice and simple. Good idea having separate cooling circuit for it and the 45° threaded insert.

• Heat flux is highest at vane cut-back but due to much larger area of vane sides, the total power applied to bulk vane is similar to total power to vane ends. Have you calculated to power distributions of each feature within a section?

Comments on Ana Megia’s Work (2)

(RFQ-1010-05_Megia.pdf andRFQ cooling ESSB _extended.pdf)

• There will be significant cooling applied to each slug tuner which will help remove heat. Even if you don’t model the slugs in the eigenmode solver, you should include their cooling in the thermal solver.

• We have slightly changed the cooling pocket layout to make it more symmetrical with respect to the vacuum port cooling manifold, which will alter things slightly.

(ignore the pi-mode stabiliser rods: redundant design)

Comments on Ana Megia’s Work (3)

(RFQ-1010-05_Megia.pdf andRFQ cooling ESSB _extended.pdf)

• Unsure why your simulations imply that the RFQ cannot be cooled sufficiently with water at sensible temperatures...

• What are your criteria for a well cooled RFQ?

• Displacement of vane-tips toward each other should be <20µm.

• Temperature gradients in your models seem to be small (<10°C?) so thermal displacements shouldn’t be too large...