CAEN November 15, 2002 Vandelli W. 1

Test Conditions

Prototype fed by CAEN Module 2527 through 100 m long cables From channels status page on generator we can report:

- with every channel OFF, currents (Imon) are some A, not stable possible calibration errors on distributor?

- there is crosstalk between channels: during the setting time of one channel, output voltage of other channels (not all) fluctuates for some tens of Volt

- channel DC-DC4 shows some instability when all other channels are ON, so we have decided not to use it

Voltage an our load has been read with a digital oscilloscope LeCroy LC564A

CAEN November 15, 2002 Vandelli W. 2

We’d like to measure prototype output noise distribution: in particular pick-up noise for linear channels and switching noise for DC-DC channels

For being able to use our oscilloscope (max voltage input 400 V peak), a voltage divider, with total resistance 4.4 M and attenuation 15.8, has been used as load for prototype’s HV channel in examination

In order to measure noise distribution FFT has been performed on data directly on the oscilloscope

For being able to discriminate pick-up noise on load and the real noise of prototype we have taken some measurement with load not connected on distributor

Noise has been tested as a function of voltage setting, one channel ON or all channels ON (to check crosstalk and stability)

Measurement scopes and method

CAEN November 15, 2002 Vandelli W. 3

Amplitude of pick-up (50 Hz) and Flicker noise for single LIN channel ON at 3.5 kV

LIN0 LIN3 LIN6

50 Hz 10.1 mV 16.4 mV 20.2 mV

Flicker 19.6 mV 22.9 mV 29.2 mV

Current

on 2527

794 A 802 A 900 A

We seek for noise components in linear channels from 0 to about 10 MHz, with all other channels OFF. Most important contributions come from pick-up and flicker noise. Figure shows in green the signal in time domain and in purple in frequency domain (FFT)

LIN6

CAEN November 15, 2002 Vandelli W. 4

Noise distribution in DC-DC channels has been verified from 0 to about 10 MHz, with all other channels OFF. Most important contribution is at 125 kHz; we think that it is the converter switching frequency. This component seems to depend on the voltage setting of the channel: for DC-DC0 at 2 kV it is only 26.5 mV. Pick-up and Flicker noise are at the same level of linear channels.

Amplitude of noise at 125 kHz for single DC-DC channel ON at 3.5 kV

DC-DC0 DC-DC3 DC-DC6

125 kHz 51.8 mV 36.7 mV 37.9 mV

Current

on 2527

797 A 799 A

DC-DC0

CAEN November 15, 2002 Vandelli W. 5

DC-DC converter

only DC-DC6 at 3.5 kV

125 kHz 37.9 mV

DC-DC6 at 3.5 kV + all other unload Ch. at 4 kV

125 kHz 74.6 mV

We have looked for differences in noise between two opposite conditions: one channel ON and all channels ON.

DC-DC channel presents a meaningful increase of noise at 125 kHz when it works with all other unload channels (linear and DC-DC) at 4 kV.

DC-DC6 with all ch. ON

CAEN November 15, 2002 Vandelli W. 6

Linear channel

only LIN6 at 3.5 kV

50 Hz 20.2 mV

LIN6 at 3.5 kV + all other unload LIN Ch. at 4 kV

50 Hz 25.3 mV

LIN6 at 3.5 kV + all other unload

Ch. at 4 kV

125 kHz 68.4 mV

Linear channel shows a small increase of pick-up noise at 50 Hz when it works with all other unload linear channels at 4 kV; but, if we set ON also DC-DC channels, LIN6 channel picks up very large noise at 125 kHz.

LIN6 with all ch. ON