Press Release

Makali'i = Subaru, many eyes reinforced for the wide field view camera
Ultra sensitive CCDs unveils the unprecedented view of the universe

November 20, 2008

Reported by
Satoshi Miyazaki (PI, contact)
Yukiko Kamata
Hisanori Furusawa
HItoshi Asai (Hamamatsu Photonics)
Masaharu Muramabtu (Hamamatsu Photonics)

Key words
Fully depleted CCD, Hyper Suprime_cam (HSC)

Main text
Subaru Telescope has been showing excellence in the observational astronomy with its high image quality and wide field of view. Many prominent results were provided by Surpime-Cam, the primary focus wide field of view camera. Since its first light, Suprime-Cam achieved 10-th anniversary and started to see results from other rival cameras in other observatories. In order to stay as a front runner, we are in need of more sensitivity with Suprime-Cam.

The R&D program of highly sensitive CCD started some years ago in collaboration between National Astronomical Observatory of Japan and Hamamatsu Photonics. The existing CCD has insufficient depletion layer in the silicon layere where the photoelectron effect occurs, resulting in the loss of longer wavelength light. Thicker depletion layer is a key for sensitivity improvement. We used a special silicon material that has higher resistance, improved the processing and assembly, and succeeded in achieving fully depleted CCD that has a depletion layer ten times thicker. The mass production is also feasible. This new CCD enebles twice sensitive observations at 1 micron wavelength.

We installed 10 of these fully depleted CCDs into Suprime-Cam after thorough lab test, and conducted first light observations in July 2008. After the performance is verified, Suprime-Cam went right into the open-use. Improvement in the sensitivity is squared in the integration time, therefore 2 times in the sensitivity means the observation time reduced to a quarter. The observation will go much faster with this new camera. This enables the study of the deep universe, such as the search for the first born object in this universe.

NAOJ group is now designing next generation camera Hyper Suprime-Cam (HSC) that boasts a field of view 10 times larger than Suprime-Cam. The focal plane extends 60 cm in diameter and requires 120 CCDs. Mass production of the new fully-depleted CCD promises the stable supply of this many CCDs. This is a critical path for the speedy development of Hyper Suprime-Cam utilizing domestic industry. With this new camera, the researchers will challenge a major problem in the current astronomy, the dark energy. Hyper Suprime-Cam on Subaru Telescope will give great advantage to the Subaru users in this very competitive field.

The fully depleted CCD will surely boost the frontier of the astronomy. In addition to the high sensitivity in the optical wavelengths, this CCD is also sensitive in the high energy X-ray. Already the next X-ray satelite group has decided to install this CCD for their telescope. Medical application is possible such as in PET. Sensitive CCD means less radiation, which is preferable for the clients that need PET diagnosis.

The release will explain how the CCD is developed and give more details in the application in astronomy.

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