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2520 pulse degradation when connecting to cryogenics

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Joined: November 23rd, 2011, 8:55 am
Country: Saudi Arabia

2520 pulse degradation when connecting to cryogenics

Post by zahedmk » November 23rd, 2011, 9:02 am

Our main objective is to pump the laser diode in the cryogenic chamber of ST-500-1-(2CX-2FO-2MW50) utilizing the Keithely pulsed laser diode system (Model 2520 which comes with a special 15 ohm characteristic impedance input cable with very low inductance). If we connect the Keithley input cable to the low frequencey coaxial probe arms of the cryogenic station to pump the laser, we are introducing the impedence mismatch (as the cryogenic arm has 50 ohm characteristic impedance) and cable inductance of the cryogenic arm into our input pulse. This is severely degrading our input pulse and we are unable to work at input currents >500mA and pulse width <20us which becomes unacceptable for our experiment. We could not take the input cables of Keithley all the way into the chamber and join force and sense cable at the probe tips as the chamber is vaccum sealed. I would appreciate if you could share with me a simple possible way to improve the pulse shape and limitations. We have also tried all the measurement consideration tips provided in the Keithley 2520 user manual but could not improve the pulse. Kindly, advise me as to how to maintain the pulse shape if connecting to other equipments.

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Joined: June 5th, 2012, 8:09 am
Country: United States

Re: 2520 pulse degradation when connecting to cryogenics

Post by KyleClifton » June 5th, 2012, 9:34 am

It sounds like you need some sort of impedance matching circuit. Try searching the web for something along those lines. Perhaps a tunable transformer would do the trick, or even a torroidal wound inductor in an LC circuit.

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