Sns Extraction Kicker System and First Article Bpfn Test. Page: 2 of 4
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Table 2: BPFN design parameter requirement
from the BPFN into the matching resistor Rm and two
coaxial cables.Rd 6.25ohm PFNi=6.25 ohm
Ls
( L PFN2=6.25 ohm
-I Rm
I, IT T I, I3 FIRST ARTICLE BPFN DESIGN
3.1 BPFN Design
In order to reduce maintenance radiation risk and to
maintain the kicker system easily, the PFN is moved from
the accumulator ring tunnel to the PFN building. A
Blumlein type Pulse Forming Networks (BPFN) was
chosen as the High Voltage Pulse Modulator. Two 50 Q
coaxial cables connected in parallel transfer current pulse
to the magnet from BPFN. Figure 2 shows the Blumlein
type Pulse Forming Network circuit principle. Two PFNs
with 6.25 Q impedance are connected in series as BFPN.
A high power fast switch thyratron is picked to discharge
the energy stored in the BPFN. A 25 Q high power
resistor, Rm is connected across the BPFN output to the
two 50 0 cables. This resistor has two functions. One is to
match the two 50 Q coaxial cables in order to present a 25
2 resistor as required for the damping of the coupling
impedance resonance in the kicker magnet. The second
function is to absorb the whole BPFN energy. A
saturating inductor, Ls is inserted between the matching
resistor Rm and BPFN output. This saturating inductor
has two functions. One function is to shorten the magnet
pulse current rise time [3], and the other is to isolate the
coupling between the BPFN and the 25 matching resistor
when the beam is accumulating in the ring, in order to
minimize the beam transverse coupling impedance.
3.2 BPFN Main parts Chosen
3.2.1 BPFN Capacitor
Two PFNs with 6.25 Q impedance are connected as
Blumlein type pulse forming network. Each PFN consists
of a 15 sections of LC network. A high voltage capacitor
is chosen as the energy storage capacitor. The PFN
capacitors are made by General Atomics, with a very low
inductance, around 15nH. The cap capacitance is 5nF. The
voltage rating is 50KV with a 50% reversal voltage.
3.2.2 High Power Fast Switch
A Marconi thyratron, model CX1925X, (Figure 3) was
chosen as the high power fast switch to discharge energyFigure 2: BPFN diagram
Figure 3: CX1925X thyratron picture.
3.2.3 High Power Resistor
The 25 Q matching resistor, Rm consists of twelve
ceramic resistor discs. Each disc is 125 mm in diameter
and 25.4 mm thick. The resistor stack is shown in figure
4.
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Mi, J.; Pai, C.; Davino, D.; Hahn, H.; Lambiase, R.; Lee, Y. Y. et al. Sns Extraction Kicker System and First Article Bpfn Test., article, June 3, 2002; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc735015/m1/2/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.