ISIS: In-situ Storage Image Sensor

In-situ Storage Image Sensor is a device that suits the requirements for the vertex detector at the future International Linear Collider (ILC), combining the charge storing capabilities of the Charge-Coupled Devices (CCD) with readout commonly used in CMOS imagers.

ILC beam structure

The ILC beam structure is shown in the right figure, with 1 ms of collisions followed by 199 ms of quiet time. The sensors have to read out approximately 20 times during a single bunch train. It is essential for the vertex detector to be as thin and light as possible, with a target thickness of 0.1% X₀ per layer. This severely limits the cooling options (ruling out liquid coolant) hence limits the permissible power dissipation. The ISIS design tackles the problem by storing the hit information in the pixel level and reading out at a slow rate during the quiet time. This indicates the advantage of ISIS:

· It minimizes the peak power by slow and continuous readout and avoids the power cycle in each bunch train;

· There is no mechanical complication of pulsed currents in a 4-5 T magnetic field comparing to other fast-readout sensor design.

The proof of principle device ISIS1 was produced in a large feature size CCD process in 2006 and successfully tested in 2007. The results were published as a NIM paper in June 2009.

The first ISIS device implemented in a small feature size CMOS sensor, ISIS2 was produced in 2008 and a lot of studies are going on. The recent results (presentation, report) were shown at DESY PRC November 2009.

Updated 27 November 2009by Yiming Li

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