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Previous minutes and documentation available at:
<http://tdweb.fnal.gov/HINS>

Meeting minutes of Oct 4^th^ 2005

L. Giobatta -- Spoke Cavity Construction

> Lanfranco mentioned some issues about the Spoke cavities construction.
> He spoke with M. Kanzie from Argonne about using the ANL tooling for
> the single spokes EP. There may be some issues. Giobatta will
> investigate. Also he mentioned that some welding for the Argonne
> cavities was done in house, and he will investigate whether the same
> welding can be done at FNAL.
>
> **I.Gonin -- RF Design of Spoke Cavities at beta=0**
>
> [*Link to
> file*](http://tdweb.fnal.gov/HINS/MeetingMinutes/2005/20051004/Ivan_October_4.ppt)
>
> Ivan presented 3 alternative design for the beta=0.4 spoke cavities: a
> solution with a single spoke, with 2 parallel spokes and with 2
> perpendicular spokes. This was motivated by the desire to use antenna
> couplers and the fact that in the perpendicular spoke option there is
> no region with null magnetic field where it would be convenient to
> place the coupler. In the single spoke design the distribution of
> fields is the usual one, and Ivan optimized the shape to
> Epeak/Eacc\~3.84 and Bpeak/Eacc\~5.97. In the perpendicular double
> spoke design, the cross-section of the spoke is a race-track and Ivan
> optimized to Epeak/Eacc\~3.56 and Bpeak/Eacc\~6.29. In both cases the
> field profile is rather flat. In the parallel 2 spoke case, there is a
> problem with the F2 mode at 326 MHz (the fundamental F1 is simulated
> at 325.03 MHz) and Ivan optimized to Epeak/Eacc\~3.01 and
> Bpeak/Eacc\~7.66. In summary, Ivan found the following table:
>
> ![](media/image2.png){width="5.320833333333334in"
> height="1.0541666666666667in"}
>
> For comparison, the Bm in the ANL cavities is \~100 mT. The main
> advantage of the single spokes and parallel spokes is the length, at a
> price of a much higher Bm.
>
> For the triple spokes cavities, Ivan simulated the ANL cavities
> rescaled to 325 MHz, and found Epeak/Eacc\~3.65 and Bpeak/Eacc\~9.17,
> and an initial simulation of FNAL Triple spokes cavities provides
> Epeak/Eacc\~3.22 and Bpeak/Eacc\~6.85 with the following table:
>
> ![](media/image3.png){width="5.375in" height="0.7826388888888889in"}
>
> The inpression is that perpedindicular double spokes can be used, even
> in view of Timer's presentation (following).

### T. Khabibouline -- RF Design of Spoke Cavities at beta=0.4

[*Link to
file*](http://tdweb.fnal.gov/HINS/MeetingMinutes/2005/20051004/Timer_Couplers_2005_10_04.ppt)

> Timer presented calculations on the cold power couplers. He started
> from the files with Em and Bm provided by Ivan and summarized again
> here:
>
> ![](media/image4.wmf)
>
> where he highlighted the maxima of E and B fields. For the single
> spoke design (beta=0.4) he computed the power dissipation of the
> antenna as a function of the Q of the cavity at 26 mA. For a design
> Q\~450k, he finds losses of the order of \~8 W (pulsed power). In the
> perpendicular double spoke cavities, Timer was able to find a region
> with very low magnetic field in which the power coupler can be located
> perpendicularly to a spoke. In that "magic" position he gets losses of
> \~10 W (pulsed power). For the parallel spokes again, he finds losses
> of \~10 W (pulsed power). In conlcusion it appears that the
> perpendicular double spokes is viable, with the only drawback that the
> length of the cavity is quite long, but with the advantage of very low
> Em and Bm. Bill proposed to assume a limited electric and magnetic
> field, and see the "real estate" investment to achieve a given
> acceleration. Finally Timer presented a conceptual design for a power
> coupler tester, based on the idea to test to antennas in a wave-guide
> 1 m long, 0.5 m high and 8 cm wide.