Plasma cleaning a new method of ultra cleaning detector cryostats
This presentation is the property of its rightful owner.
Sponsored Links
1 / 24

Plasma Cleaning A new method of ultra-cleaning detector cryostats PowerPoint PPT Presentation


  • 113 Views
  • Uploaded on
  • Presentation posted in: General

Plasma Cleaning A new method of ultra-cleaning detector cryostats. Sebastian Deiries, Armin Silber, Olaf Iwert, Evi Hummel, Jean Louis Lizon European Southern Observatory ESO ( http://www.eso.org ). Introduction. Why cleaning of CCD cryostats?

Download Presentation

Plasma Cleaning A new method of ultra-cleaning detector cryostats

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Plasma cleaning a new method of ultra cleaning detector cryostats

Plasma CleaningA new method of ultra-cleaning detector cryostats

Sebastian Deiries,

Armin Silber, Olaf Iwert,

Evi Hummel, Jean Louis Lizon

European Southern Observatory ESO (http://www.eso.org)

SDW2005: Plasma Cleaning S. Deiries, ESO


Introduction

Introduction

  • Why cleaning of CCD cryostats?

  • Contamination is more a problem with optical than IR detectors blue wavelengths

  • Conventional cleaning (mechanical, with detergent, isopropyl-alcohol, acetone & baking) insufficient?

  • Plasma cleaning used in industry for ultra cleaning

  • It is a simple method with easy installation:First results after a few days!

  • It is rather cheap and has very low cleaning costs

  • It gives very high efficient cleaning results

  • The risks are low

SDW2005: Plasma Cleaning S. Deiries, ESO


Conventional cleaning

Conventional Cleaning

  • Before plasma cleaning can be applied, the piece or cryostat should roughly be clean. Normally we apply our standard cleaning processes:

  • mechanicalcleaning,

  • ultrasonic cleaning with special

  • detergents,

  • chemical cleaning with isopropyl

  • alcohol or acetone

  • baking in vacuum oven

Chemicals and detergents for ultrasonic and chemical cleaning

Precautions and careful handling of the chemicals

Baking of cryostat parts in the vacuum oven depending from the material up to 160 o C

Cryostat part in ultrasonic bath

(See also “Ultra-clean CCD Cryostat – CCD contamination can be kept under control” from S. Deiries, SDW2002)

SDW2005: Plasma Cleaning S. Deiries, ESO


Cryostat components after conventional cleaning

Cryostat components after conventional cleaning

My colleague Armin Silber had the idea to introduce

Plasma cleaning as a final ultra cleaning step:

Because cryostat looks clean after conventional cleaning: but there are still (organic) contaminations on the surface.

SDW2005: Plasma Cleaning S. Deiries, ESO


Plasma cleaning process

Plasma cleaning process

Application: Removal of very thin films of oil, oxides and greases

  • During plasma cleaning the surface is cleaned

  • physically by ion bombardment (like sand-blasting)

  • chemically e.g. by active oxygen (oxidation and reduction).

SDW2005: Plasma Cleaning S. Deiries, ESO

The surface is cleaned physically by ion bombardment and UV radiation and chemically by active oxygen.

The surface is cleaned physically by ion bombardment and UV radiation and chemically by active oxygen.


Plasma cleaning a new method of ultra cleaning detector cryostats

Realization of Plasma cleaning

Existing vacuum oven, refurbished to a plasma oven

SDW2005: Plasma Cleaning S. Deiries, ESO


Plasma cleaning a new method of ultra cleaning detector cryostats

SDW2005: Plasma Cleaning S. Deiries, ESO


High voltage plasma controller lfg40 from company diener

High voltage plasma controllerLFG40 from company Diener

http://www.dienerelectronic.de

High voltage control

Plasma control

Pressure

regulation

0.1 – 1 mBar

Voltage display

Plasma regulation

SDW2005: Plasma Cleaning S. Deiries, ESO


Plasma cleaning a new method of ultra cleaning detector cryostats

Plasma cleaning devices

Modified vacuum oven, equipped with a high voltage anode

Powerful dry vacuum pump:Alcatel ACP28

High voltage plasma controller LFG40

SDW2005: Plasma Cleaning S. Deiries, ESO


Use of different gases

Use of different gases

  • Oxygen - Best for cleaning of aluminium and stainless steel

  • Ambient air- Sufficient for normal cleaning

  • Argon - Cleaning without chemical reaction

  • Hydrogen - Best for cleaning of gold, silver and copper

  • Nitrogen - Similar as Argon

  • Flour-containing gases- Chemical cleaning

  • Mixtures of the gases mentioned above

SDW2005: Plasma Cleaning S. Deiries, ESO


Special arrangement plasma cleaning inside every assembled cryostat

Special arrangement: Plasma Cleaning inside everyassembled cryostat

High Voltage Anodemounted outside on the cryostat window

Controller Diener Electronic LFG40

Cryostat

No disassembly

necessary !

Trans-former

(Diener)

Ground cablefixed at the case

SDW2005: Plasma Cleaning S. Deiries, ESO


Plasma cleaning a new method of ultra cleaning detector cryostats

Plasma cleaning devices

Successful plasma cleaning inside the assembled OmegaCam cryostat

After some minutes the large volume (approx. 200 l) of the cryostat was filled

by a violet glowing plasma.

A normal cleaning process takes not longer than 10 minutes!

SDW2005: Plasma Cleaning S. Deiries, ESO


Omegacam cryostat during plasma cleaning

OmegaCam cryostat during plasma cleaning

SDW2005: Plasma Cleaning S. Deiries, ESO


Plasma cleaning a new method of ultra cleaning detector cryostats

Videofrom Plasma ignition

and cleaning

SDW2005: Plasma Cleaning S. Deiries, ESO


Safety measures

Safety measures

  • Exhaust gases should not go to the working laboratory (small toxic risk)

  • UV radiation is absorbed by oven window

  • Electrical safety

SDW2005: Plasma Cleaning S. Deiries, ESO


Plasma cleaning a new method of ultra cleaning detector cryostats

Plasma cleaning costs

Procurement costs:

Vacuum oven~8000 EUR

Diener Electronic

LFG40 Plasma Controller~5000 EUR

Vacuum pump 7000 EUR

Maintenance:

Electrical costs per cleaning process0.20 EUR

Costs of special gases~200 EUR per annum

Maintenance>100 EUR per annum

SDW2005: Plasma Cleaning S. Deiries, ESO


Materials cleaned by plasma

Materials cleaned by plasma

(Coated) Epoxy fiber glass

Gold plated copper

PCBs

Aluminum

Stainless

steel

SDW2005: Plasma Cleaning S. Deiries, ESO


Limitations with plasma cleaning

Limitations with plasma cleaning

  • Plastic materials and PCBsshould not be plasma-treated longer than 10 minutes; risk of becoming black

  • Damage of CCD detectors?Test ongoing; which of the manufacturer present at the SDW2005 is interested and would supply a sample CCD?

SDW2005: Plasma Cleaning S. Deiries, ESO


Plasma cleaning a new method of ultra cleaning detector cryostats

How to handle plasma cleaned parts

A plasma cleaned cryostat part must be handled strictly under clean-room condition to avoid recontamination.

SDW2005: Plasma Cleaning S. Deiries, ESO


Test of cleaning result

Test of cleaning result

  • Water drop method:

    A sample, which is contaminated shows a round water drop on its surface. After the plasma cleaning there is less adhesion, therefore no water drop on the surface possible: the water is flowing away.

contaminated

Plasma cleaned

SDW2005: Plasma Cleaning S. Deiries, ESO


Test of cleaning result1

Test of cleaning result

  • End vacuum test:

    Typical vacuum end pressure values of ESO standard cryostats (after 1h pumping time):

    Before plasma cleaning: 1 x 10E-3mBar

    After plasma cleaning: 5x 10E-5mBar

SDW2005: Plasma Cleaning S. Deiries, ESO


Plasma cleaning a new method of ultra cleaning detector cryostats

Test of cleaning result:

  • Mass-spectrum test:

Water

Many lines disappear or are reduced significantly

CO

CO2

O2

SDW2005: Plasma Cleaning S. Deiries, ESO


Conclusions

Conclusions

  • Very effective cleaning of (hidden) contaminants as an addition to conventional cleaning

  • Fast Cleaning method

  • Successful cleaning of assembled cryostats (OmegaCam)

SDW2005: Plasma Cleaning S. Deiries, ESO


Many thanks for listening

Many Thanks for Listening

SDW2005: Plasma Cleaning S. Deiries, ESO


  • Login