20.9.2010 © 2010 universitÄt rostock | fakultÄt informatik und elektrotechnik q ext estimations...

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