Creating Buffer front end circuit to read AD744 output signal

Hi all,

i don't have so much experience in circuit design and/or simulation.

This is my situation:

I have a PMT tube connected to a nuclear scintillation detector that makes available a test point that delivers semigaussian pulses.

Before the test point there is an AD744 with its output connected to a 10nF capacitor and after there is 1K resistor that goes to GND, from this node of connection of capacitor/resistor there is a 4.7k resistor that goes to the TEST POINT.

Here comes my question:

I must read this signal with my ADS1675REF board that has as front end a THS4503 (attached pic).

I can use differential input on attached circuit or put one of two input to GND to make a single ended front end input stage.

But in both situations clearly if i put the TEST POINT in input of that THS4503 circuit the weak pulses drop off and i cannot see any signal.

I really appreciate if you can give me any suggestion on circuit to make to create a suitable buffer to read signal coming from this test point?

Thanks in advance.