[Acc_sem_comm] Possible Accel. Seminar

[Fanglei Lin]

I support it.

Fanglei
________________________________
From: Acc_sem_comm <acc_sem_comm-bounces at jlab.org> on behalf of Kevin Jordan <jordan at jlab.org>
Sent: Wednesday, October 21, 2020 12:08 PM
To: Gianluigi Ciovati <gciovati at jlab.org>
Cc: Acc_Sem_Comm at jlab.org <Acc_Sem_Comm at jlab.org>
Subject: Re: [Acc_sem_comm] Possible Accel. Seminar

Looks good to me,
Kevin

Sent from my iPad

On Oct 20, 2020, at 5:24 PM, Gianluigi Ciovati <gciovati at jlab.org> wrote:


Dear all,
please see below a suggested speaker, title and abstract for an Accel. Seminar. Please let me know if you agree by Thursday.

Thanks,
Gigi

________________________________
From: Garcia, Cougar A [US] (MS) <Cougar.Garcia at ngc.com>
Sent: Tuesday, October 20, 2020 5:12 PM
To: Gianluigi Ciovati <gciovati at jlab.org>; Steven Mark Anlage <anlage at umd.edu>
Cc: Talanov, Vladimir V [US] (MS) <Vladimir.Talanov at ngc.com>
Subject: [EXTERNAL] RE: EXT :Re: Fwd: Fw: Invitation for an Accelerator Seminar at Jefferson Lab


Dr. Ciovati,



Of course! here is my abstract from ASC that covers what I would talk about:



Title: Correlation of complex surface impedance and vortex dynamics in Nb thin films of varying quality

Authors: Cougar Garcia, Alex Sirota, Vladimir Talanov, Anna Herr

Abstract:

            It is important to characterize both the RF properties and vortex dynamics of thin films for superconducting device and circuit applications that operate in low magnetic field environments, and determine the circuit performance. Using a Parallel Plate Resonator Technique (PPR) [Taber1990], it has been shown the average vortex pinning constant (

<image001.png>
and viscosity (
<image002.png>
) can be extracted from the RF surface impedance measurements as a function of applied perpendicular magnetic field ([Pambianchi1993], [Golosovsky1994]). To date, only two groups ([Janjusevic2006], [Kwon2018]) have measured these properties for Niobium thin films, which is commonly used in superconducting devices and circuits. For electronics applications all of the important vortex dynamics occur near the critical temperature (Tc); however, the earlier work only characterized these properties at low temperature. In this work, we measured complex surface impedance of 200-nm thick Nb films and extracted the vortex pinning constant and viscosity in the framework of the Coffey-Clem unified theory as a function of temperature and magnetic field. Our samples had a range of Ginzburg-Landau parameter (
<image003.png>
), and, for
<image004.png>
, typical values of vortex pinning constant, viscosity, and RF surface resistance at 10 GHz and 5 mT were 2 kN/m^2, ~1e-8 N-s/m^2, and 1.2
<image005.png>
near the critical temperature (~0.85Tc), respectively. The vortex parameters and surface resistance (
<image006.png>
) values agree well with [Janjusevic2006] and [Kwon2018], and the surface impedance as a function of Ginzburg-Landau parameter and its implications on flux trapping will be discussed.





Thanks,



Cougar



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