MICROWAVE KINETIC INDUCTANCE DETECTOR

Sanath prasad13mmt1044

INTRODUCTION

Microwave Kinetic Inductance Sensor (MKID) a type of superconducting photon detector.

Developed by scientists at the California Institute of Technology and the Jet Propulsion Laboratory in 2003.

They are being developed for high-sensitivity astronomical detection for frequencies ranging from the far-infrared to X-rays.

Kinetic inductance ???

Due to kinetic energy of charged particles.

Kinetic inductance is observed in high carrier mobility conductors (e.g. superconductors) and at very high frequencies.

Is dominant only in case of thin conducting films.

Consider cylindrical cross section of volume A and length L.

Consist of charge carriers moving with same velocity v and charge density be ne.

i=AneV

V=i/Ane

Kinetic energy =1/2 mv2

So Ek = ½ (m n A L) (i/Ane)2

EK= ½{ Lm/Ane2 } i2

LK = KINETIC INDUCTANCE.

Kinetic Inductance is Lot like resistance.

L/A*m/ne2

How MKID works……

Photons incident on a strip of superconducting material break Cooper pairs and create excess quasiparticles.

LK α 1/density

The kinetic inductance of the superconducting strip is inversely proportional to the density of Cooper pairs.

Thus the kinetic inductance increases upon photon absorption.

This inductance is combined with a capacitor to form a microwave resonator.

The resonant frequency changes with the absorption of photons.

Incident photons change the surface impedance of a superconductor through the kinetic inductance effect.

The kinetic inductance effect occurs because energy can be stored in the supercurrent of a superconductor.

Reversing the direction of the super current requires extracting this stored energy, which yields an extra inductance.

This change can be accurately measured using a thin film superconducting

Resonant circuit, resulting in a measurement of the energy and arrival time of the incident photon for the case of near-IR to X-ray photons, or the total photon flux for lower energy photons

•

Is a thin film device

• Large format imaging array at 1thz-3thz

Has superc0nducting transmission line operating at few giga hz

Capacitivily coupled to the side of the lines are the thin film resonators

When x ray comes it gets absorbed in the tantalum

•It breaks superconducting pairs

Produces a large share of quasi particle

•This get injected into the resonator

• The resonator chages its freequency .

• So we can find the presence of that particle

• In other word an effective temp variation in the system

BRIEFLY……

Microwave Kinetic Inductance Detectors: Resonators

Superconductors below a critical temperature Tc have electrons divided in two different populations:

The Cooper Pairs, electrons bound together with an energy E=2D3.528*kbTc by the electron-phonon interaction. They act as superconducting carriers.

The Quasi-Particles, single electrons which act as carriers in a normal metal.

In this two fluids model the total conductivity of the material is:

= 1(nQP) - j 2(nCP)𝜎 𝜎And the complex surface impedance is

Temperature vs quasi particle generation

Film thickness vs kinetic inductance

ENERGY BAND DIAGRAM

MULTIPLEXING MKID

MATERIALS AND ENVIORNMENT REQUIERD

APPLICATIONS

Further steps…

• The next steps are• Further optimization of the single pixel (a new mask is already

under test).• Development of KIDs on membranes to check the possibility

of using them on balloon-borne and space missions.

REFERENCES

• Benjamin A. Mazin Department of Physics, University of California, Santa Barbara, CA 93106.