View source for CDC old & new preamp noise scope trace study

A study was performed using three preAmps:

* Yves' old preAmp : the old preamp that changed behavior a month ago
* Beni's old preAmp: the old preamp used before by Beni.
* Naomi's preAmp   : the new preAmp.

<b> Left is always Yves' old preAmp, middle is Beni's old preAmp, right is Naomi's new preAmp </b> 
[except mentioned differently]

First 2000V was put on the chamber and a random cosmic ray signal was selected: 

{| border="1" cellpadding="2"
|width="415pt"|[[Image:signal_yves_2000.jpg|thumb|none|400px|Yves' old preamp - 2000V - cosmic ray]]
|width="415pt"|[[Image:signal_beni_2000.jpg|thumb|none|400px|Beni's old preamp - 2000V - cosmic ray]]
|width="415pt"|[[Image:signal naomi_2000.jpg|thumb|none|400px|Naomi's new preamp - 2000V - cosmic ray]]
|}


OK, so far so good. Let's switch the HV off and look at the ringing: the highest amplitude ringing was selected, 
so you are looking at the high end of the pedestal:

<b>Channel 1</b>
{| border="1" cellpadding="2"
|width="415pt"|[[Image:ringing_yves_ch1.jpg|thumb|none|400px|Yves' old preamp - ch1 - ringing]]
|width="415pt"|[[Image:ringing_beni_ch1.jpg|thumb|none|400px|Beni's old preamp - ch1 - ringing]]
|width="415pt"|[[Image:ringing naomi_ch1.jpg|thumb|none|400px|Naomi's new preamp - ch1 - ringing]]
|}
<b>Channel 8</b>
{| border="1" cellpadding="2"
|width="415pt"|[[Image:ringing_yves_ch8.jpg|thumb|none|400px|Yves' old preamp - ch8 - ringing]]
|width="415pt"|[[Image:ringing_beni_ch8.jpg|thumb|none|400px|Beni's old preamp - ch8 - ringing]]
|width="415pt"|[[Image:ringing naomi_ch8.jpg|thumb|none|400px|Naomi's new preamp - ch8 - ringing]]
|}
<b>Channel 9</b>
{| border="1" cellpadding="2"
|width="415pt"|[[Image:ringing_yves_ch9.jpg|thumb|none|400px|Yves' old preamp - ch9 - ringing]]
|width="415pt"|[[Image:ringing_beni_ch9.jpg|thumb|none|400px|Beni's old preamp - ch9 - ringing]]
|width="415pt"|[[Image:ringing naomi_ch9.jpg|thumb|none|400px|Naomi's new preamp - ch9 - ringing]]
|}
<b>Channel 15</b> <- This channel is always used for Fe-55 measurements
{| border="1" cellpadding="2"
|width="415pt"|[[Image:ringing_yves_ch15.jpg|thumb|none|400px|Yves' old preamp - ch15 - ringing]]
|width="415pt"|[[Image:ringing_beni_ch15.jpg|thumb|none|400px|Beni's old preamp - ch15 - ringing]]
|width="415pt"|[[Image:ringing naomi_ch15.jpg|thumb|none|400px|Naomi's new preamp - ch15 - ringing]]
|}

The old preAmp has higher amplitude noise in chip2 -> channels 9-16
The new preamp has lower amplitude ringing compared to the old preAmp.



Now it comes: wierd peaks (see below) are seen in the Fe-55 spectra in yves' old preAmp and Beni's old preAmp. 
We see those peaks because those spectra were taken when the straw was self triggering.
{| border="1" cellpadding="2"
|width="415pt"|[[Image:Fe_amplitude_2100V_old_preamp_30819.jpg|thumb|none|400px|Yves' old preamp - Fe-55 - with weird peaks around channel 1000. The peak on the left might be the ringing shown above.]]
|width="415pt"|[[Image:Fe_amplitude_2100V_beni_old_preamp.jpg|thumb|none|400px|Beni's old preamp - Fe-55 - with weird (double) peaks around channel 1000]]
|}

This is how it looks on the scope: (the new preAmp did not show this behavior)
<b>Channel 1</b> 
{| border="1" cellpadding="2"
|width="415pt"|[[Image:peak_yves_ch1.jpg|thumb|none|400px|Yves' old preamp - ch1 - weird peak]]
|width="415pt"|[[Image:peak_beni_ch1.jpg|thumb|none|400px|Beni's old preamp - ch1 - weird peak]]
|}
<b>Channel 8</b> 
{| border="1" cellpadding="2"
|width="415pt"|[[Image:peak_yves_ch8.jpg|thumb|none|400px|Yves' old preamp - ch8 - weird peak]]
|width="415pt"|[[Image:peak_beni_ch8.jpg|thumb|none|400px|Beni's old preamp - ch8 - weird peak]]
|}
<b>Channel 9</b> 
{| border="1" cellpadding="2"
|width="415pt"|[[Image:peak_yves_ch9.jpg|thumb|none|400px|Yves' old preamp - ch9 - weird peak]]
|width="415pt"|[[Image:peak_beni_ch9.jpg|thumb|none|400px|Beni's old preamp - ch9 - weird peak]]
|}
<b>Channel 15</b> <- channel used for Fe-55 measurements
{| border="1" cellpadding="2"
|width="415pt"|[[Image:peak_yves_ch15.jpg|thumb|none|400px|Yves' old preamp - ch15 - weird peak]]
|width="415pt"|[[Image:peak_beni_ch15.jpg|thumb|none|400px|Beni's old preamp - ch15 - weird peak]]
|}

The HV board was also changed but this did not make any difference. We think this behavior is a sign 
that the old preAmp is broken.

<b> These peaks were not seen in yves' old preAmp months ago. We know this because at at some point we
had to increase the internal threshold of the straw to do Fe-55 measurements with the old preAmp.
Also, they would have showed up in the Fe-55 spectra (see below)</b>

<b> Question remains: what happened to go from this situation: </b>
{| border="1" cellpadding="2"
|width="415pt"|[[Image:Fe_amplitude_2100V_old_preamp_30599.jpg|thumb|none|400px|amplitude: Yves' old preamp months ago, 55Fe, 50/50 Ar/CO2, 2100V, 2009]]
|}

<b> to this </b>
{|
|width="415pt"|[[Image:Fe_amplitude_2100V_old_preamp_30819.jpg|thumb|none|400px|amplitude: Yves' old preamp, 55Fe, 50/50 Ar/CO2, 2100V, 2010]]
|}