Since we have problem of TAMA PSD, we considered to buy new PSD. Matteo asked two PSD from HAMAMATSU company for test. They are C10443-03 (we call it 03 later) and C10443-04 (we call it 04 later). The information of them can be found from this link.

From the datasheet, 03 and 04 PSD only have difference in position. I think the integrated noise spectrum can represent a position resolution. If so, the one with better position resolution should have a lower noise spectrum. Therefore, I firstly tested 03 which has a better position resolution. If it is better than the old PSD, we should use it in the future.

Together with Matteo, we made a customized circuit based on Mammoth connectors, bananna connectors and lemo connectors. In this way, the eight channels from HAMAMATSU PSD can be connected to power supply and ADC of DGS system. Four channels from PSD are used for power supply, which contain one plus(12V), one minus(-12V) ,and two grounds. Another four channels are called x1, x2, y1, and y2 separatly. The experimental set-up is shown in attached figure 1.

To convert four signal channels into pitch and yaw, I realized a matrix inside simulink file. This matrix is enclosed in a block called 'BS_test', as shown in the attached figure2.

Since old measurements have been saved in DGS system, I just plot new PSD data with old ones. As shown in the attached figure 3, there is comparison between old low gain TAMA PSD and 03PSD. We can see

1. REF0/1 (BS angular motion sensed by low gain TAMA PSD) is comparable with REF16/17 (BS angular motion sensed by 03PSD). This means that two PSD have the same gain.

2. REF8/9 (electronic noise of low gain TAMA PSD) is lower than REF24/25 (electronic noise of 03PSD).

3. Red lines in this figure shows the ADC noise. Actually this measurement is a bit strange. It shows that ADC noise is even higher than the electronic noise of low gain TAMA PSD. This can be correct if the ADC noise really becomes worse by itself.

4. Since the Red lines overlap with REF 24/25, it means the measured electronic noise maybe just ADC noise. So if we want to check better mirror angular motion, we need to amplify the signals coming from PSD.

I also compared the electronic noise between high gain TAMA PSD with 03PSD. The result is shown in the attached figure 4. Red lines are 03PSD electronic noise, which is lower than REF8/9 (high gain TAMA PSD electronic noise). 

We will also test 04 PSD to justify the relationship between PSD position resolution and noise spectrum.