Dear Colleagues,

It is with deep sadness that I inform you of the passing of our dear friend and colleague, Michael Lehnen, after a long and courageous battle with illness. Michael was not only a kind and friendly colleague but also an embodiment of our CARE values. He was an internationally renowned expert in disruption physics and mitigation.

Michael's career was marked by his exceptional leadership in research, particularly in the DMS (Disruption Mitigation System) activity. The numerous collaborations he fostered were highly effective and leave a significant legacy for the Science Division and the ITER Project to uphold and build upon. His contributions to the DMS development were of the highest calibre, playing a crucial role in the successful DMS final design review held last March. Despite facing severe medical challenges, Michael's preparation and delivery of the masterful DMS Physics Basis presentation at the FDR demonstrated his remarkable character, competence, and dedication.

Michael will be profoundly missed by all of us at ITER and by the international fusion community. 

All united, we express our most sincere condolences to those closest to Michael and to all of his many colleagues and friends.

It was always a pleasure to work with Michael on experiments across the world, as a member of the ITER Disruption Task Force, ITPA, and organizing numerous meetings with him over the past decade and more. He was a unifying force within our field, patient but persistent. I feel blessed and honored to have been able to see him one last time for a few good days in Japan this past April. My heartfelt condolences go out to his family. Michael was a good man whom we will sorely miss.

Michael was my first technical mentor at FZ Juelich 20 years ago when I started my PhD thesis at TEXTOR. He introduced me into the thermal helium beam technique and shared openly his expertise to me as a new student. His passion for fusion and for guiding early career students and scientists was always an outstanding trade of Michael. I always enjoyed working with him and I am deeply saddened to hear about this loss for his family, friends and the entire fusion community. Rest in peace Michael.

Michael's reputation as a leading figure in the study of disruptions and, more specifically, in the development and application of disruption mitigation techniques, was, of course, well-known for many years prior to his recruitment to the ITER Organization. However, it was only after he joined the IO to lead the physics R&D, design and development activities for the ITER Disruption Mitigation System that we fully appreciated what an outstanding researcher we had gained. During the decade that Michael led the ITER activities supporting the development of the DMS, he demonstrated a deep understanding of the critical physics issues and the ability to cast them in a quantitative framework to guide the research and design studies. He also possessed the profound insight (and diplomatic skills!) required to develop the wide-ranging research collaborations across the fusion community which were established to address the key challenges in the development of ITER's DMS. His research during this period confirmed his standing as an internationally recognized leader in his field and the central figure in the major effort undertaken by the ITER project to resolve the challenge of developing an adequate disruption mitigation capability to ensure reliable operation of ITER. Despite the increasing seriousness of his illness, Michael demonstrated significant personal courage in maintaining his work at the forefront of the ITER DMS research and design activities, and in providing leadership to the project's work in this area.

But Michael was much more than an outstanding scientist. He had a delightful and open personality and an engaging, mischievous sense of humour. It was a great pleasure to work with him and a privilege to learn from his deep knowledge and expertise. I was deeply saddened to hear of his passing - it is a major loss to his many friends and colleagues in the international fusion community, as well as to the ITER project, and we recognize that we have lost a uniquely talented individual. I would like to convey my deepest condolences to those closest to Michael and to his friends and colleagues.

I was deeply saddened to hear of the passing of my dear mentor Michael. Throughout my PhD at CEA Cadarache, our monthly meetings were invaluable. I always respected his warmth, deep subject knowledge, and his remarkable combination of expertise with humility and approachability. Michael will be greatly missed as a scientist, mentor, and a wonderful human being. My deepest condolences go out to his friends and family. May he rest in peace.

Words cannot express how saddened I am by this news. He is such a kind person to students and colleagues, and contributed a lot to our fusion society with his outstanding work. May Michael Lehnen pass in peace.

Michael has also been a very good friend to me since we shared the office in the barracks in the Forschungszentrum Jülich. 25 years ago, during our doctoral thesis at TEXTOR.  We did study the plasma boundary layer properties in the tokamak with different techniques. Later. we often lived in the same house during our secondments to JET during EFDA times exploring JET with graphite and metallic wall. In our free time, we did a lot of things together with our families and other Jülich colleagues at JET and formed a special community as "expats". Hiking was one of Michael's passions, for example there were legendary tours in Wales with Alexander Huber, Stefan Jachmich, Mathias Brix and myself. After his move to ITER to solve the disruption mitigation issue, we remained friends and often visited each other with our families. Michael was an epicurean, an excellent cook and an attentive host. His dry, sometimes wicked sense of humour was as much a hallmark of his character as his friendliness and helpfulness. I am very sad that Michael has passed away so soon and I will miss him very much. He will certainly be remembered as one of my good friends, not only by me, but also by many colleagues who knew him.

My deep condolences to Michael's family, friends, and colleagues. Michael has been a friend, mentor, an excellent physicist and manager. I have admired his ability to engage in-depth with numerous projects at once while keeping an always upbeat attitude. We have been fortunate to enjoy his guidance, wisdom and humor. We will miss you.

Michael's passing away is a tragic loss for his colleagues and the fusion community as a whole. He was a prominent figure in the field of disruptions and was considered by many of us as "the voice of ITER" on this topic. His dedication to addressing the issue fuelled many experiments, simulations and technology developments throughout the world. I first met him while I was doing my PhD, when he warmly welcomed me in the disruption mitigation team at JET. I owe him my first presentations in task force E meetings, and also my continued interest for the topic. I will remember his ability to hear people's opinions out, his patience with newcomers, and his witty sense of humour. The best tribute we can pay him is to continue his work.

First of all, I would like to express my deepest condolence for Michael and his family. Needless to say, it is such a loss and Michael has been one of the great leaders at ITER IO and done lots of critical research work including DMS Taskforce and ITPA. He also has been a good friend of the KSTAR team and couple of years ago, I've enjoyed a lot discussing plasma runs with him at KSTAR control room and lively chat with him drinking beer. I wish his family and friends get over the absence of him well.

I am deeply saddened by the disappearance of Michael, who was both a colleague and a friend during his post-doctoral years at Tore Supra and later at ITER. Michael was always dedicated, helpful, and, of course, highly competent. I remember a PSI conference in 2006 or 2008, which he attended with his partner and their newborn baby. It was a natural and joyful moment, and everyone was made happy by having a baby at the conference. Michael will be missed by many, and I have a special thought for his children and partner.

We were deeply saddened to hear about Michael's passing and we'd like to send our deepest condolences to his family, friends, and colleagues around the world. Not only in the ITER research community but also in the European fusion devices Michael was an outstanding figure with deep knowledge on various fields of physics, especially on plasma disruptions. Most recently, he was actively involved in shattered pellet injection (SPI) experiments on JET and ASDEX Upgrade, in charge of coordinating the most complicated ones of these where several pellets should be injected in a timely manner into the plasma. This was a brilliant example of a task where his devotion and passion towards science helped in solving any outstanding problem that at first sight looked impossible to be circumvented. But hard work put on the activity paid off resulting in high-quality scientific results for numerous journal articles and conference contributions. Michael leaves behind an honourable legacy in the field of disruption physics and big boots to be filled. The image of a wryly but warmly smiling Michael will stay fondly imprinted in our memory for years to come.

I was shocked and very sad to read about Michael's passing. He was an outstanding scientist and a great colleague and comrade during our time together at JET. I often enjoyed his dry sense of humour when we took a short break from our control room duties in the adjacent fish bowl cafeteria and I will always remember him, our colleague Stefan and myself standing together in the lunch queue, towering over the other colleagues and quite literally having a "high level" chat. I'll always cherish those memories. My thoughts are with his family and friends during this difficult time.

It is with a great sadness that I learned about Michael's passing away and I am deeply touched. Last time I was in close contact with him was when he coordinated different disruption studies that we performed at COMPASS for ITER. Before that, I knew him from JET and despite the fact we were not working in the same field of physics and the we met rarely, he always had time for nice conversations. He was an extremely nice and kind person with a big smile. My sincere condolences to his family and closest.

I was very saddened to learn about Michael's passing away while at a US fusion program meeting.   It was announced at our meeting which reflects the impact that Michael's work had on our field. I personally remember fondly discussing disruption mitigation with Michael for the past 15 years and appreciated his skillful leadership in moving the ITER disruption mitigation system to a mature design.  His memory will be etched in so many minds that continue to strive for fusion energy.

It was sad to learn the news about Michael Lehnen. I met him many times over the years at ITER meetings and disruption workshops. I was very impressed how much effort and energy he contributed to planning the ITER disruption mitigation system. I differed with him on some aspects of disruptions, but he politely heard me out. His contributions will be important in the operation of ITER and development of magnetic fusion energy.

We are deeply saddened by the loss of Michael Lehnen. He was a beloved and esteemed colleague. We particularly remember our collaboration around the exploitation of the Dynamic Ergodic Divertor at TEXTOR within the Trilateral Euregio Cluster. Our deepest sympathy and condolences are with his close family and friends.

It is with great sadness that I learned of Mickael's death. I had the chance to work with him to set up contracts. Always friendly, humble and attentive. My sincere condolences to his family, friends and colleagues.

With sincere condolences to Michael's family, friends and colleagues.

We lost a good friend and superb scientist, whose service to international fusion community, dedication and proven leadership, commitment to helping others will always be remembered.

Rest in a peace, Michael.

It is with great sadness that I have learned of this news. I will always remember the times we worked together to set up the project to install a Shattered Pellet Injector at JET in support of the ITER design as part of an international cooperation. Michael's contribution to the project and the execution of this unique set of experiments was of prime importance and crucial for the design of the ITER Disruption Mitigation System. I wish to express my sincere condolences to his family, friends, colleagues and loved ones.

Dear Mr.Lenhan, 

Thank you for your visit to Naka Institute in April - which just a two month ago and I could meet Mr.Lenhen even briefly, very tall and he had a good smile and therefore I was supprised to hear the news.

Our sincere condolences for your sudden loss.

Please let us pray that he may rest in peace.

We will deeply miss you as a lovely person and energetic expert.

It has been a great pleasure to work with you Michael. You will be deeply missed as a fellow physicist and as a friend. We will carry on your works.

Michael, the last few years with you and your kind smile are something I will never forget. I wish you eternal peace without any more pain. It was truly a fortune to have worked with you.