20.9.2010 © 2010 universitÄt rostock | fakultÄt informatik und elektrotechnik q ext estimations...
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20.9.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK
Qext estimations for the
"Broad-Hook"-HOM coupler
H.-W. Glock
Universität Rostock - Institut für Allgemeine Elektrotechnik
20.9.2010
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"Classical" LEP hook design as starting point (priv.com. WW)
20.9.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock 2
coaxial 50-Ohm-port(connector not modelled)
adjustable capacitive coupling
combined E-/H-field coupling,capacity couples to outer conductor
support carries liquid helium
reminder
320.9.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK U. van Rienen – H.-W. Glock 3
E-field geometry @ 704 MHz
strong capacitive coupling between "hook" and outer conductor
capacitive coupling at hook determines notch resonance frequency
reminder
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Pure hook not tunable for 704 MHz => Modification of hook end in order to adjust fundamental mode notch filter
20.9.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock 4
enlarge capacitive coupling at hook with additional surface element
reminder
520.9.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock 5
Waveguide(TM0)–Coax–Transmission blocked @ fundamental mode frequency => Tuning ok
reminder
620.9.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock 6
Q-ext estimations based on:
CSC-coupling of 8 modes in D=130mm-coupler-cavity-connection (TE11,TM01, TE21,TM11,TE01)
couplers left-right mirrored-symmetric (But: cavity asymmetric, no coupler calc for D=140mm-pipe up to now)
D=80mm beam pipes left open (but most below cut-off)
720.9.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock 7
This (cst-computation, csc-concatenation, q-fit-proc.) gives:
Q_fundamental 3.0 10^8
much steeper Q(f) decrease than filter-free coax, BUT: still to high 1-1.5 GHz
Is it possible to put coupler port closer to cavity waist (cav.design used from 21.7.2010)
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Our attempts to improve coupling
20.9.2010 © 2010 UNIVERSITÄT ROSTOCK | FAKULTÄT INFORMATIK UND ELEKTROTECHNIK H.-W. Glock 8
23/02/2010
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increase penetration depth: but poor effect, not nice for dark current
flip hook to come closer to cavity: but total changeof filter behaviour, not tuned yet